AVERTISSEMENT : Assurez-vous de bien suivre les
instructions données dans cette notice pour réduire au
minimum le risque d’incindie ou d’explosion ou pour
éviter tout dommage matériel, toute blessure ou la mort.
WARNING: If the information in these instructions
is not followed exactly, a fire or explosion may
result, causing property damage, personal injury,
or death.
• HOT GLASS WILL CAUSE
BURNS.
• DO NOT TOUCH GLASS
UNTIL COOLED.
• NEVER ALLOW CHILDREN
TO TOUCH GLASS.
• UNE SURFACE VITRÉE CHAUDE
PEUT CAUSER DES BRÛLURES.
• LAISSER REFROIDIR LA SURFACE
VITRÉE AVANT D'Y TOUCHER.
• NE PERMETTEZ JAMAIS À UN ENFANT
DE TOUCHER LA SURFACE VITRÉE.
• EL VIDRIO CALIENTE
CAUSARÁ QUEMADURAS.
• USTED DEBE NUNCA
TOCAR EL VIDRIO CALIENTE.
• LOS NIÑOS DEBEN NUNCA
TOCAR EL VIDRIO.
- Do not store or use gasoline or other flammable
vapors and liquids in the vicinity of this or any other
appliance.
- WHAT TO DO IF YOU SMELL GAS:
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use any
phone in your building.
• Immediately call your gas supplier from a
neighbor’s phone. Follow the gas supplier’s
instructions.
• If you cannot reach your gas supplier, call the fire
department.
- Installation and service must be performed by a
qualified installer, service agency or the gas supplier.
- Ne pas entreposer ni utilizer d’essence ni d’autres vapeurs
ou liquides inflammables dans le voisinage de cet appareil
ou de tout autre appareil.
- QUE FAIRE SI VOUS SENTEZ UNE ODEUR DE GAZ :
• Ne pas tenter d’allumer d’appareil.
• Ne touchez à aucan interrupteur. Ne pas vous servir des
téléphones se trouvant dans le bâtiment où vous trouvez.
• Appelez immédiatement votre fournisseur de gaz depuis
un voisin. Suivez les instructions du fournisseur.
• Si vous ne pouvez rejoindre le fournisseur de gaz,
appelez le service des incindies.
- L’installation et l’entretien doivent être assurés par un
installateur ou un service d’entretien qualifié ou par le
fournisseur de gaz.
MPD Direct-Vent
Gas Fireplaces
P/N 506015-07 Rev. NC 05/2012
This manual is one of a set of two supporting this product.
Refer to P/N 506017-06 for Care and Operation Instructions.
Ce manuel est disponible en francais, simplement
en faire la demande. Numéro de la pièce 506223-43.
INSTALLER: Leave this manual with the appliance.
CONSUMER: Retain this manual for future reference.
INSTALLATEUR : Laissez cette notice avec l’appareil.
CONSOMMATEUR : Conservez cette notice pour
consultation ultérieure.
This appliance may be installed in an aftermarket permanently located, manufactured home (USA only) or mobile
home, where not prohibited by local codes. This appliance is only for use with the type of gas indicated on the rating
plate. This appliance is not convertible for use with other gases, unless a certified kit is used.
The Millivolt appliances have a millivolt gas
control valve with piezo ignition system. If
any optional accessories that will require
electrical power are to be installed, the
electrical power must be provided at the time
of appliance installation.
The Electronic appliances are designed
to operate on natural or propane gas. An
electronic intermittent pilot ignition system
provides safe, efficient operation. External
electrical power is required to operate these
units. In the event of a power outage, four (4)
"AA" batteries (in battery holder) provide
backup power for appliance operation
(excluding [optional] blower).
These vented gas fireplace heaters are sealed
combustion, air-circulating gas fireplaces
designed for residential applications.
Approved Vent Components
These fireplaces are designed, tested and
listed for operation and installation with the
following vent components only:
• Secure Vent® Direct-Vent System
Components manufactured by Security
Chimneys International,
• Secure Flex® Flexible Vent Components
manufactured by Security Chimneys
International and
• Z-FLEX® Model GA Venting Systems listed
to UL1777 and ULCS635 manufactured by
Flexmaster Canada Limited.
Use only the correct size venting (4 1/2 in.
inner and 7 1/2 in. outer).
These approved vent system components are
labeled for identification. DO NOT use any
other manufacturer’s vent components with
these appliances.
GENERAL INFORMATION
WARNING
Young children should be carefully supervised when they are
in the same room as the appliance. Toddlers, young children
and others may be susceptible
to accidental contact burns. A
physical barrier is recommended
if there are at risk individuals in
the house. To restrict access to
a fireplace or stove, install an
adjustable safety gate to keep
toddlers, young children and
other at risk individuals out of
the room and away from hot
surfaces.
AVERTISSEMENT
Les jeunes enfants devraient être
surveillés étroitement lorsqu’ils
se trouvent dans la même pièce
que l’appareil. Les tout petits,
les jeunes enfants ou les adultes
peuvent subir des brûlures s’ils
viennent en contact avec la surface chaude. Il est recommandé
d’installer une barrière physique
si des personnes à risques habitent la maison. Pour empêcher
l’accès à un foyer ou à un poêle,
installez une barrière de sécurité; cette mesure empêchera les
tout petits, les jeunes enfants et
toute autre personne à risque
d’avoir accès à la pièce et aux
surfaces chaudes.
Children and adults should be alerted to
the hazards of high surface temperature
and should stay away to avoid burns or
clothing ignition.
Les enfants et les adultes devraient
être informés des dangers que posent
les températures de surface élevées
et se tenir à distance afin d’éviter des
brûlures ou que leurs vêtements ne
s’enflamment.
DO NOT ATTEMPT TO ALTER OR MODIFY
THE CONSTRUCTION OF THE APPLIANCE
OR ITS COMPONENTS. ANY MODIFICATION
OR ALTERATION MAY VOID THE WARRANTY, CERTIFICATION AND LISTINGS OF
THIS UNIT.
2
Page 3
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
WARNING
I m p ro pe r i n s ta ll at i o n ,
adjustment, alteration, service
or maintenance can cause injury
or property damage. Refer to
this manual. For assistance or
additional information consult
a qualified installer, service
agency or the gas supplier.
WARNING
Failure to comply with these
installation instructions will
result in an improperly installed
and operating appliance, voiding
its warranty. Any change to this
appliance and/or its operating
controls is dangerous.
WARNING
Clothing or other flammable
material should not be placed
on or near the appliance.
AVERTISSEMENT
On ne devrait pas placer de
vêtements ni d’autres matières
inflammables sur l’appareil ni à
proximité.
WARNING
Any safety screen or guard
removed for servicing the
appliance must be replaced
prior to operating the appliance.
AVERTISSEMENT
Tout écran ou protecteur retiré
pour permettre l’entretien de
l’appareil doit être remis en
place avant de mettre l’appareil
en marche.
WARNING
Improper installation or use of
this appliance can cause serious
injury or death from fire, burns,
explosion or carbon monoxide
poisoning.
WARNING
Failure to position the parts in
accordance with these diagrams
or failure to use only parts
specifically approved with this
appliance may result in property
damage or personal injury.
AVERTISSEMENT
Risque de dommages ou de
blessures si les pièces ne sont
pas installées conformément à
ces schémas et ou si des pièces
autres que celles spécifiquement
approuvées avec cet appareil sont
utilisées.
Note: Installation and repair should be
done by a qualified service person. The
appliance should be inspected before use
and at least annually by a professional
service person. More frequent cleaning
may be required due to excessive lint from
carpeting, bedding material, etcetera. It
is imperative that control compartments,
burners and circulating air passageways of
the appliance be kept clean.
Remarque: L’installation et la
réparation devrait être confiées à un
technicien qualifié. L’appareil devrait
faire l’objet d’une inspection par un
technicien professionnel avant d’être
utilisé et au moins une fois l’an par la
suite. Des nettoyages plus fréquents
peuvent être nécessaires si les tapis,
la literie, et cetera produisent une
quantité importante de pous-sière. Il
est essentiel que les compartiments
abritant les commandes, les brûleurs
et les conduits de circulation d’air de
l’appareil soient tenus propres.
Do not use these appliances if any part
has been under water. Immediately
call a qualified, professional service
technician to inspect the appliance
and to replace any parts of the control
system and any gas control which have
been under water.
Ne pas utiliser cet appareil s’il a été
plongé, même partiellement, dans
l’eau. Appeler un technicien qualifié
pour inspecter l’appareil et remplacer
toute partie du système de commande
et toute commande qui a été plongée
dans l’eau.
Only trim kit(s) supplied by the
manufacturer shall be used in the
installation of this appliance.
Seules les trousses de garniture
fournies par le fabricant doivent être
utilisées pour l’installation de cet
appareil.
These appliances comply with National
Safety Standards and are tested and listed
by OMNI-Test Laboratories, Inc. (Report
No. 116-F-13-4) to ANSI Z21.88-2009 (in
Canada, CSA-2.33-2009), and CAN/CGA-
2.17-M91(R2009) in both USA and Canada,
as vented gas fireplace heaters.
Both millivolt and electronic versions of
these appliances are listed by OMNI-Test
Laboratories for installation in bedrooms
and Manufactured Homes.
Misc. Codes / Standards
The Installation must conform to local codes
or, in the absence of local codes, with the
National Fuel Gas Code, ANSI Z223.1-2009
/ NFPA 54—latest edition (In Canada, the
current CAN/CSA-B149.1 installation code).
The appliance, when installed, must be
electrically grounded and wired in accordance
with local codes or, in the absence of local
codes, with the National Electrical Code,
ANSI/NFPA 70—latest edition, or the
Canadian Electrical Code, CSA C22.1—
latest edition.
Provide adequate clearances around
air openings and adequate accessibility
clearance for service and proper operation.
Never obstruct the front or back openings of
the appliance.
These appliances are designed to operate
on natural or propane gas only. The use
of other fuels or combination of fuels will
degrade the performance of this system and
may be dangerous.
These fireplaces are designed as supplemental
heaters. Therefore, it is advisable to have an
alternate primary heat source when installed in
a dwelling.
These appliances must not be connected to a
chimney or flue serving a separate solid fuel
burning appliance.
Both millivolt and electronic systems can be
operated during a power outage, and feature
manually operated hi-low flame control. The
BTU Input for these appliances is shown in
Table 1.
Models
MPD33
MPD35
MPD40
MPD45
Table 1: Input (BTU/HR) Gas Valves
(Millivolt and Electronic)
Input Rate (BTU/HR)
Nat. GasProp. Gas
17,500 high
11,700 low
20,000 high
12,800 low
27,000 high
18,500 low
29,000 high
20,500 low
17,500 high
14,000 low
20,000 high
15,200 low
27,000 high
21,500 low
29,000 high
22,500 low
3
Page 4
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Gas Pressure—All Models
Tables 2 and 3 show the appliances' inlet and
manifold gas pressure requirements:
Fuel #MinimumMaximum
Natural
Gas
Propane
4.5 in. WC
(1.12 kPa)
11.0 in. WC
(2.74 kPa)
10.5 in. WC
(2.61 kPa)
13.0 in. WC
(3.23 kPa)
Table 2: Inlet Gas Supply Pressure
Fuel #LowHigh
Natural
Gas
Propane
1.6 in. WC
(0.40 kPa)
6.3 in. WC
(1.57 kPa)
3.5 in. WC
(0.87 kPa)
10.0 in. WC
(2.49 kPa)
Table 3: Manifold Gas Supply Pressure
Test gauge connections are provided on
the front of the millivolt and electronic gas
control valve (identified IN for the inlet and
OUT for the manifold side). The control
valves have a 3/8 in. (10 mm) NPT thread
inlet and outlet side of the valve (refer to
Figures 1 and 2).
Propane tanks are at pressures that will
cause damage to valve components. Verify
that the tanks have step down regulators to
reduce the pressure to safe levels.
The appliance and its appliance main gas
valve must be disconnected from the gas
supply piping system during any pressure
testing of that system at test pressures in excess of 1/2 psi (3.5 kPa).
The appliance must be isolated from the
gas supply piping system by closing its
equipment shutoff valve during any pressure
testing of the gas supply piping system at
test pressures equal to or less than 1/2 psi
(3.5 kPa).
Orifice Sizes—Sea Level to High Altitude
(All Models)
These appliances are tested and approved
for installation at elevations of 0–4500 ft
(0–1372 m) above sea level using the
standard burner orifice sizes (marked with an
"*" in Table 4). For elevations above 4500 ft,
contact your gas supplier or qualified service
technician.
Deration—At higher elevations, the amount
of BTU fuel value delivered must be reduced
by either:
• Using gas that has been derated by the gas
company.
• Changing the burner orice to a smaller
size as regulated by the local authorities
having jurisdiction and by the (USA)
National Fuel Gas Code NFPA 54—latest
edition / ANSI Z223.1-2009 or, in Canada,
the CAN/CSA-B149.1 codes—latest
edition.
4
Install the appliance according to the
regulations of the local authorities having
jurisdiction and, in the USA, the National
Fuel Gas Code NFPA 54—latest edition /
ANSI Z223.1-2009 or, in Canada, the CAN/
CSA-B149.1—latest edition.
Flame breadth, height and width will diminish
4% for every 1,000 feet of altitude. Gas Valve
Diagrams. See Figure 1 for Millivolt models
and Figure 2 For Electronic Models.
In Canada - CAN/CGA-2.17-M91 (R2009)
(high altitude): THE CONVERSION SHALL
BE CARRIED OUT BY A MANUFACTURER’S
AUTHORIZED REPRESENTATIVE, IN
ACCORDANCE WITH THE REQUIREMENTS
OF THE MANUFACTURER, PROVINCIAL
OR TERRITORIAL AUTHORITIES HAVING
JURISDICTION AND IN ACCORDANCE
WITH THE REQUIREMENTS OF THE
CAN/CGA-B149.1 OR CAN/CGA-B149.2
INSTALLATION CODES.
REQUIREMENTS FOR THE
COMMONWEALTH OF MASSACHUSETTS
These fireplaces are approved for installation
in the US state of Massachusetts if the
following additional requirements are met:
• Install this appliance in accordance with
Massachusetts Rules and Regulations
248 C.M.R.
Main Gas Control Knob
OFF/PILOT/ON
N
O
T
O
it
L
I
P
O
F
F
OUT
IN
Manifold Pressure Tap
Inlet Pressure Tap
Figure 1: SIT Millivolt Gas Valve
(from DFC Wire Harness)
Inlet (IN) Test Port
Manifold (OUT) Test Port
Orange Wire
(from DFC Wire
Harness)
Main Gas Inlet
3/8 in. NPT
Figure 2: SIT Electronic Gas Valve
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Pilot Adjustment
I
P
W
O
L
H
I
HI/LO Variable
Flame Height
Adjustment
Green Wire
Screw
T
O
L
HTPTHTPT
Model
Series
MPDT33
MPDR33
MPD35
MPD40
MPD45
Nat.Gas
drill size (inches)
#37 (0.104 in.)*
24M10•
#45 (0.0820 in.)*
39L66•
#38 (0.1015 in.)*
99K76•
#47 (0.0785 in.)*
99K74•
* Standard size installed at factory
• Part /Cat. Number
Propane
drill size (inches)
0.048 in.
99K78•
#55 (0.0520 in.)*
19L52•
0.063 in.
21L01•
#52 (0.0635 in.)*
37G00•
Table 4: Burner Orifice Sizes
Elevation 0–4500 ft ( 0–1372 m)
• Installation and repair must be done by
a plumber or gas fitter licensed in the
Commonwealth of Massachusetts.
• The exible gas line connector used shall
not exceed 36 in. (92 cm) in length.
• The individual manual shut-off must be a
T-handle type valve.
Massachusetts Horizontal Vent Requirements
in the Commonwealth of Massachusetts,
horizontal terminations installed less than
seven (7) feet above the finished grade
must comply with the following additional
requirements:
• A hard wired carbon monoxide detector
with an alarm and battery back-up must
be installed on the floor level where the
gas fireplace is installed. The carbon
monoxide detector must comply with
NFPA 720, be ANSI/UL 2034 listed and be
ISA certified.
• A metal or plastic identication plate must
be permanently mounted to the exterior
of the building at a minimum height of
eight (8) feet above grade and be directly
in line with the horizontal termination.
The sign must read, in print size no less
than one-half (1/2) inch in size, GAS VENT
DIRECTLY BELOW. KEEP CLEAR OF ALL
OBSTRUCTIONS.
Hi/Lo Flame
Control Knob
Yellow Ground Wire
(from DFC Wire Harness)
Page 5
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
COLD CLIMATE INSULATION
For cold climate installations, seal all cracks
around your appliance with noncombustible
material and wherever cold air could enter
the room. It is especially important to
insulate outside chase cavity between studs
and under floor on which appliance rests, if
floor is above ground level. Gas line holes
and other openings should be caulked or
stuffed with unfaced fiberglass insulation.
If the fireplace is being installed on a
cement slab in cold climates, a sheet of
plywood or other raised platform can be
placed underneath to prevent conduction
of cold transferring to the fireplace and into
the room. It also helps to sheetrock inside
surfaces and tape for maximum air tightness
and caulk firestops.
MANUFACTURED HOME
REQUIREMENTS
This appliance may be installed in
an aftermarket permanently located,
manufactured home and must be installed
in accordance with the manufacturer's
instructions.
Cet appareil peut être installé cómme
du matériel d'origine dans une maison
préfabriquée (É.U. seulement) ou mobile
et doit être installé selon les instructions
du fabricant.
This appliance is only for use with the type
of gas indicated on the rating plate. This
appliance is not convertible for use with other
gases, unless a certified kit is used.
Cet appareil doit être utilisé uniquement
avec le type de gaz indiqué sur la plaque
signalétique. Cet appareil ne peut être
converti à d'autres gaz, sauf si une
trousse de conversion est utilisée.
CAUTION: Ensure that the cross
members are not cut or weakened
during installation. The structural
integrity of the manufactured home
floor, wall, and ceiling / roof must be
maintained.
CAUTION: This appliance must
be grounded to the chassis of the
manufactured home in accordance with
local codes or in the absence of local
codes, with the National Electrical Code
ANSI / NFPA 70—latest edition or the
Canadian Electrical Code CSA C22.1—
latest edition.
REAR VENT
APPLICATION
TOP VENT
APPLICATION
APPLICATION
TOP VENT
INSTALLATION
VERTICAL VENT
(Rear Vent Application)
HORIZONTAL VENT
(Rear Vent Application with a chase)
RECESSED
REAR VENT
APPLICATION
TOP VENT
TOP VENT
APPLICATION
TOP VENT
APPLICATION
HORIZONTAL VENT
(Rear Vent Application without a chase)
APPLICATION
TOP VENT
APPLICATION
HORIZONTAL VENT
(Top Vent Application)
Figure 3: Typical Locations
LOCATION
In selecting the location, the aesthetic and
functional use of the appliance are primary
concerns. However, vent system routing to
the exterior and access to the fuel supply are
also important.
Due to high temperatures, the appliance
should be located out of traffic and away
from furniture and draperies (Figure 3).
En raison des températures élevées,
l’appareil devrait être installé dans
un endroit où il y a peu de circulation et loin du mobilier et des tentures
(Figure 3).
The location should also be free of electrical,
plumbing or other heating/air conditioning
ducting.
These direct-vent appliances are uniquely
suited for installations requiring a utility shelf
positioned directly above the fireplace. Utility
shelves like these are commonly used for
locating television sets and decorative plants.
VERTICAL VENT
(Top Vent Application)
Be aware that this is a heat producing
appliance. Objects placed above the unit
are exposed to elevated temperatures.
Do not insulate the space between the
appliance and the area above it (see
Figure 8).
The minimum height from the base of the
appliance to the underside of combustible
materials used to construct a utility shelf in
this fashion is shown in Figure 8.
The appliance must be mounted on a
fully supported base extending the full
width and depth of the unit. The appliance
may be located on or near conventional
construction materials. However, if installed
on combustible materials, such as carpeting,
vinyl tile or other combustible material other
than wood flooring, the appliance shall be
installed on a metal or wood panel extending
the full width and depth of the appliance.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
5
Page 6
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
LOWEST DISCHARGE OPENING OF VENT
TERMINATION HEIGHTS FOR VENTS ABOVE
VENT TERMINATION CLEARANCES
These instructions should be used as a
guideline and do not supersede local
codes in any way. Install venting according
to local codes, these instructions,
the current National Fuel Gas Code
(ANSI-Z223.1-2009) in the USA or the
current standards of CAN/CSA-B149.1 in
Canada.
Vertical Vent Termination Clearances
Terminate multiple vent terminations
according to the installation codes listed
above and Figures 4 and 5.
12 in.
(305mm)
Minimum
Figure 4: Multiple Terminations
Vertical Vent Termination Clearances
The vent / air intake termination clearances
above the high side of an angled roof are as
Horizontal Overhang
2 FT MIN.
Termination
Storm Collar
Flashing
Concentric
Vent Pipe
FLAT OR SLOPED ROOFS
Vent
*H = MINIMUM HEIGHT FROM ROOF TO
2 FT
MIN.
Lowest
Discharge
Opening
H*
1 inch (25.4 mm) Minimum
Clearance to Combustibles
Vertical
Wall
X
12
Roof Pitch is X/12
Figure 5: Termination Heights for Vents
Above Flat or Sloped Roofs
The horizontal vent termination must have a minimum of 6 in. (152 mm) clearance to any
overhead combustible projection of 2 1/2 in. (64 mm) or less, see Figure 6. For projections
exceeding 2 1/2 in. (64 mm), see Figure 6. For additional vent location restrictions, refer to
Figure 7 on Page 7.
Horizontal Vent Termination Clearances
Combustible Projection
inches or less in length
2-1/2
Combustible Projection greater
than 2-1/2 inches in length
Ventilated
Soffit
Unventilated
Soffit
18"
(457 mm)
12"
(305 mm)
Side Elevation View
Termination Kit
Figure 6: Horizontal Vent
Termination Clearances
6"
(152 mm)
All horizontal terminations
may be located as close as
6” (152mm) to any
(non-combustible and
combustible) exterior
sidewall. This distance
may be decreased to 2”
(51mm) for non-combustible exterior
sidewalls only, if the
SV4.5HT-2 termination
is used.
Termination Kit
Note: See Figure 34 on Page 20 for the exterior wall recess
allowances of the square horizontal termination.
6
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Page 7
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
MINIMUM CLEARANCES TO COMBUSTIBLES
Appliance And Vent Clearances
The appliance is approved with zero clearance to combustible
materials on all sides (as detailed in Table 5), with the following
exception: When the unit is installed with one side flush with a wall,
the wall on the other side of the unit must not extend beyond the
front edge of the unit. In addition, when the unit is recessed, the side
walls surrounding the unit must not extend beyond the front edge of
the unit (see Figure 3).
Hearth Extension—A hearth extension is not required with this
appliance. If a hearth extension is used, do not block the lower control
compartment door. Any hearth extension used is for appearance only
and does not have to conform to standard hearth extension installation
requirements.
Shelf Height—To provide for the lowest possible shelf surface, use
the alternate rear vent outlet, the venting attached to the top vent
should be routed in a way to minimize obstructions to the space above
the appliance. Do not insulate the space between the appliance and the area above it (seeFigure 8). The minimum height from the base
of the appliance to the underside of combustible materials used to
construct a utility shelf in this fashion is shown in Figure 8.
The appliance should be mounted on a fully supported base extending
the full width and depth of the unit. The appliance may be located on
or near conventional construction materials. However, if installed on
combustible materials, such as carpeting, vinyl tile, etc., a metal or
wood barrier covering the entire bottom surface must be used.
1/2 in. (13 mm)
Back
0 in. (0 mm) from Spacers Or
Dimples
1/2 in. (13 mm)
Sides
0 in. (0 mm) from Spacers Or
Dimples **
3 in. (76 mm)
Top of Fireplace
0 in. (0 mm) with standoff(s) in
vertical position (see Figure 11)
Floor0 in. (0 mm)
From Bottom of Unit To Ceilingminimum of 64 in. (1626)
Vent
3 in. (76 mm) Top* / 1 in. (25.4 mm)
Sides & Bottom
SERVICE CLEARANCES Feet (meters)
Front3 ft (0.9 m)
Table 5: Minimum Clearances*
*Note: 3 in. (75 mm) above any horizontal/inclined vent component.
**Note: See Page 10, Step 1 for clearance requirements to the nailing
flange located at each side of the unit and any screw heads adjacent to it.
Do not insulate the
space between the
appliance and the area
above it.
Combustible Shelf Height—in. (mm)
Do not insulate the
space between the
appliance and the
area above it.
Shelf Height
(see table)
Figure 8:
Shelf Height Minimum Clearances
8
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Page 9
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
12 (305) MANTEL
10 (254) MANTEL
8 (203) MANTEL
6 (152) MANTEL
4 (102) MANTEL
4
(102)
14
(356)
12
(305)
10
(254)
2 (51) MANTEL
TOP OF
APPLIANCE
6
(152)
NOTE - Hood shown as positioned in louvered
front model. The hood position in the flush
faced front model is lower than shown.
8
(203)
MANTEL CLEARANCES
Inches (mm)
Wall Finishes / Surrounds / Mantels
Note: Combustible wall finish materials and/or surround materials must not be allowed to encroach the area defined by the appliance front face (black
sheet metal). Never allow combustible materials to be positioned in front of or overlapping the appliance face (see Figures 65 and 66 on Page 34).
Non-combustible materials, such as surrounds and other appliance trim, may be installed on the appliance face with these exceptions: they must not
cover any portion of the removable glass panel or control compartment.
Vertical installation clearances to combustible mantels vary according to the depth of the mantel. See Figure 9. Mantels constructed of
non-combustible materials may be installed at any height above the appliance opening; however, do not allow anything to hang below the
fireplace hood.
Minimum clearance requirements include any projections such as shelves, window sills, mantels, etc. above the appliance.
NOTE: We recommend the use of high temperature paint (rated 175 °F, or higher) on the underside of the mantel.
At 6 in. minimum
side wall clearance,
a combustible wall
can project to any
length.
Top View of
Fireplace
Figure 9: Minimum Mantel Clearances
WARNING
Failure to position the parts in accordance with these
diagrams or failure to use only parts specifically
approved with this appliance may result in property
damage or personal injury.
AVERTISSEMENT
Risque de dommages ou de blessures si les pièces
ne sont pas installées conformément à ces schémas
et ou si des pièces autres que celles spécifiquement
approuvées avec cet appareil sont utilisées.
Combustible Materials
Allowed In Shaded Area
“Safe Zone”
Combustible Walls
shown in dark gray
Combustible materials may
project beyond either side
of the fireplace opening
as long as they are kept
within the shaded area
illustrated here.
6 in.
(152 mm)
o
45
3 1/2 in.
(89 mm)
Figure 10: Minimum Distance to Side Wall
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
9
Page 10
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
PRE-INSTALLATION STEPS
The appliance is shipped with all gas controls
and components installed and pre-wired.
Before installing the appliance, follow these
steps:
1. Remove the shipping carton.
2. Remove the shipping pad, exposing the front
glass door.
3. Open the two spring latches securing the
glass door (under the firebox floor). Remove
the door by tilting it outward at the bottom
and lifting it up. Set the door aside, taking
care to protect it from inadvertent damage.
See Removing Glass Panels on Page 32.
5. Remove the log set from the firebox. Handle
logs carefully to prevent breakage.
6. Remove the embers and volcanic stone from
the control compartment.
TYPICAL INSTALLATION SEQUENCE
The typical sequence of installation is
outlined below; however, each installation
is unique and may result in variations to the
steps described. See the pages referenced in
the following steps for detailed procedures.
Step 1. FRAMING (Page 10): Construct the
appliance framing. Position the appliance
within the framing and secure with nailing
brackets.
IMPORTANT! Bend up the appropriate
header spacing standoffs for the drywall/
finish material thickness to be used
(see Figure 11).
Bend up the outer pair for 1/2 in. materials
and the inner pair for 5/8 in. materials.
Bend out the appropriate nailing flanges for
the drywall/finish material to be used. Nailing
flanges are provided for flush framing, 1/2 in.
and 5/8 in. framing depths (see Figure 11).
Step 2. ROUTING GAS LINE (Page 12):
Route gas supply line to appliance location.
Step 3. PREPARING APPLIANCE VENT
COLLAR (MPD35/-40/-45 models with
combined top/rear vent) (Page 13).
Step 4. INSTALLING VENT SYSTEM
(Page 13): Install the vent system and
exterior termination.
Step 5. FIELD WIRING (Page 25).
a. Millivolt Appliances—Install the
operating control switch (not factory
provided). If installing the optional forced
air circulating blower, bring in electrical
service line.
b. Electronic Appliances—Field wire and
install operating control switch.
Step 6. WIRING—OPTIONAL FORCED AIR
BLOWER KIT (Page 26).
Step 7. CONNECTING GAS LINE (Page 26):
Make connection to gas supply.
Step 8. VERIFYING APPLIANCE OPERATION
Frame the appliance as illustrated in Figures
13 and 14 on Pages 10 and 11 (Figure 13
applies to corner framing installations only).
All framing details must allow for a minimum
clearance to combustible framing members
as shown in Table 5 on Page 8.
If the appliance is to be elevated above floor
level, a solid continuous platform must be
constructed below the appliance.
Headers may be in direct contact with the
appliance top standoff spacers when they are bent up vertically, maintaining the 3 in.
clearance to the fireplace top, but must not
be supported by them or notched to fit
around them. All construction above the appliance must be self-supporting. DO NOT
use the appliance for structural support.
Secure the fireplace to the side framing
members using the unit’s nailing flanges
— one top and bottom on each side of the
fireplace front. See Figure 11. Use 8d nails
or their equivalent.
Bend up the appropriate header spacing top
standoffs before installing the fireplace.
Header Spacing Top Standoffs
(two pairs on front edge of firebox top)
Lift up outer pair for
1/2 in. finish materials
Side
Framing
NOTE: The nailing flanges, combustible
members, and screw heads in areas directly
adjacent to the nailing flanges are EXEMPT
from the 1/2 in. clearance to combustible
requirements for the firebox outer wrapper.
Combustible framing may be in direct contact
with the nailing flanges and may be located
closer than 1/2 in. from screw heads and the
firebox wrapper in areas adjacent to the
nailing flanges.
Frame the opening to the exact dimensions
specified in the framing details in this manual.
Figure 11: Unit Secured to Framing by
Nailing Flange
IMPORTANT!
Lift up inner pair for
5/8 in. finish materials
Unit Nailing Flange
(No clearance to
combustible framing
is required)
10
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Page 11
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Top View
Right Side View
Front View
Framing
.oNledoMABCDE
MPDT33
MPDR33
MPD35
MPD40
MPD45
Diagrams, illustrations and photographs are not to scale. Consult installation
instructions. Product designs, materials, dimensions, specifications, colors,
and prices are subject to change or discontinuance without notice.
.ni4/133
mm
.ni
mm
.ni4/1534/15361/11124/39361
mm5985981550101604
.ni4/1044/10461/11624/34461
mm220122018767311604
.ni4/1544/10461/11624/34461
mm941122018767311604
Notes
Thermal Efficiency (%)
Fireplace
Model
MPDT33
MPDR33
MPD35
MPD40
MPD45
Natural GasPropane
AFUE EnerGuide
AFUE EnerGuide
(P4)
62456449
61536455
62536055
67596760
67596759
—37 3/4 12 7/833 1/4
—959327845845
19 5/8—12 7/833 1/4 33 1/4
498—327845845
(P4)
Based on CSA P.4.1-09
VENT FRAMING:
TOP VENT WITH ONE
90° ELBOW
VENT FRAMING:
REAR VENT WITH
NO ELBOWS
B
1/2
10-1/2
(
)
267
7
(178)
5-1/8
(130)
7
(178)
5-1/8
D
(130)
C
E
A
A
Dimension “E” is the required framing depth when the
finish material (drywall) thickness is 1/2 in. (13mm).
Framing should be
constructed of 2x4
or larger lumber.
12-1/8
(308)
12-1/8
(308)
Inches (mm)
Vertical Venting through the Ceiling
Frame ceiling opening: Use a plumb line from the ceiling above the appliance to locate center of the vertical run. Cut and/or frame an opening,
10 1/2 in. x 10 1/2 in. (267 mm x 267 mm) inside dimensions, about this center mark (see Figure 17).
3 (76)
N
Gas Inlet (either
side and bottom)
Optional Electrical Inlet
Knockout requiring a
C
B
Field-Provided Junction
Box (either side)
6 (152)
L
1-3/8 (35)
K
1/2 (13)
See Note [2].
1-5/8 (42)
M
F (rear vent
models only)
Electrical Inlet
2-3/4" x 2"
(70 x 51 mm)
Cover Plate
with Knockout
Rear/Side
Framing
Spacers
Header
Spacing
Top
Standoffs
Notes:
[1] MPD models have a top and rear vent. MPDR models
have a rear vent only. MPDT models have a top vent only.
[2] Collars protrude one inch on MPDT33 and MPDR33 models.
G
H
Concentric Flue:
Flue
4-1/2 in. (114 mm);
Combustion Air
7-1/2 in. (190 mm).
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
FIREPLACE FRAMING SPECIFICATIONS
.oNledoMABCDEF
MPDT33
MPDR33
MPD35
MPD40
MPD45
Note:
•Rear Vent Applications in Corner Installations: The horizontal vent length
(from a to b) must not exceed 28 inches (711 mm).
•MPDT33 and MPDR33 Models: Dimensions A through F occur when one
45-degree elbow is connected directly to the appliance collar.
•MPD35, MPD40, and MPD45 Models: Dimensions D through F occur when
one 45-degree elbow is connected directly to the appliance collar.
.ni8/1332/18461/54361/371
mm1482321278734616721
.ni8/1532/1758/50461/3914/3828/16
mm29816412301784037651
.ni8/10461/31623/113461/39161/11038/77
mm910145511011784977002
.ni8/1548/36661/516461/39161/3334/39
mm641168612911784348842
Figure 13: Corner Framing with Horizontal Termination
Step 2. ROUTING GAS LINE
Route a 1/2 in. (13 mm) gas line to the
left side of the appliance as shown in
Figure 14. Gas lines must be routed,
constructed and made of materials that
are in strict accordance with local codes
and regulations. All appliances are factoryequipped with a flexible gas line connector
and 1/2 in. shutoff valve. (See Step 6 on Page 25).
Left Side Front
Corner of Fireplace
Framing
Pipe Coupling
(Recommended)
6-1/2"
(152 mm)
3"
(76 mm)
Also see Figure 12.
Figure 14: Route Gas Line
Proper Sizing of Gas Line
Properly size and route the gas supply
line from the supply regulator to the area
where the appliance is to be installed per
requirements outlined in the National Fuel
Gas Code, NFPA 54—latest edition (USA) or
CAN/CSA-B149.1—latest edition (Canada).
12
24 1/45
MPD and MPDT units
MPD and MPDR units
C
Back wall of chase/enclosure (including any finishing materials)
Never use galvanized or plastic pipe. Refer to
Table 6 for proper sizing of the gas supply
line, if black iron pipe is being used. Gas lines
must be routed, constructed and made of
materials that are in strict accordance with
local codes and regulations. We recommend
that a qualified individual such as a plumber
or gas fitter be hired to correctly size and
route the gas supply line to the appliance.
Installing a gas supply line from the fuel
supply to the appliance involves numerous
considerations of materials, protection,
sizing, locations, controls, pressure,
sediment, and more. Certainly no one
unfamiliar and unqualified should attempt
sizing or installing gas piping.
Schedule 40 Pipe
Length (feet)
Natural
Gas
Propane
Gas
0–101/2 in.3/8 in.
10–401/2 in.1/2 in.
40–1001/2 in.1/2 in.
100–1503/4 in.1/2 in.
150–2003/4 in.1/2 in.
Table 6: Schedule 40 Black Iron Pipe—
Inside Diameter
Notes:
• All appliances are factory-equipped with
a flexible gas line connector and 1/2 inch
shutoff valve (see Figure 46 on Page 25).
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
b
F
7"
(178 mm)
E
D
a
A
B
• See Massachusetts Requirements on
Page 4 for additional requirements for
installations in the state of Massachusetts
in the USA.
• The gas supply line should Not be
connected to the appliance until Step 6
(Page 25).
• A pipe joint compound rated for gas
should be used on the threaded joints.
Ensure propane resistant compounds are
used in propane applications. Be very
careful that the pipe compound does not
get inside the pipe.
• It is recommended to install a sediment
trap in the supply line as close as possible
to the appliance.
• Check with local building ofcial for local
code requirements.
IMPORTANT: If propane is used, be aware
that if tank size is too small (i.e. under
100 lbs, if this is the only gas appliance
in the dwelling. Ref. NPFA 58), there
may be loss of pressure, resulting in
insufficient fuel delivery (which can result
in sooting, severe delayed ignition or other
malfunctions). Any damage resulting from
an improper installation, such as this, is
not covered under the limited warranty.
Page 13
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
A vent restrictor may be needed when
A vent restrictor may be needed when
TOP VENT SEAL AND COVER PLATE REMOVAL
WHEN USING THE TOP VENT
REAR VENT SEAL AND COVER PLATE REMOVAL
WHEN USING THE REAR VENT
Step 3. PREPARING APPLIANCE VENT
COLLAR (MPD35/-40/-45 models with
combined top/rear vent)
Each of the unit’s two vent collars are sealed
with a cover plate and a seal plate and
gasket. The cover, and seal plate and gasket
must be removed from the vent collar being
used. Refer to Figure 15 for top vent usage
and Figure 16 for rear, and the following
steps to prepare the appropriate collar
for use.
From the vent collar being used, remove the
four screws securing the vent seal plate and
gasket. Remove and discard the seal plate and
gasket.
When the top vent collar is being used,
from inside the firebox, loosen the two
screws in the keyhole slots of the cover plate
and remove the remaining two cover plate
securing screws. Remove and discard the
cover plate. Reinstall and securely tighten
all four screws.
When the rear vent collar is being used,
from inside the firebox, remove the two
screws securing the lintel to the rear wall of
the firebox, then remove the lintel. Remove
the four cover plate securing screws. Remove
and discard the cover plate.
Reinstall and securely tighten all four cover
plate screws. Re-secure the lintel to the rear
wall of the firebox.
WARNING
Failure to reinstall and securely
tighten cover plate screws could
result in leakage of flue products
into the living space. Vent cover
plate and vent seal cap must
remain securely installed on
unused vent collar. Failure to
do so could result in leakage of
flue products into living space.
Step 4. INSTALLING VENT SYSTEM
These instructions should be used as a
guideline and do not supersede local
codes in any way. Install venting according
to local codes, these instructions,
the current National Fuel Gas Code
(ANSI-Z223.1-2009) in the USA or the
current standards of CAN/CSA-B149.1
in Canada.
Ensure clearances are in accordance
with local installation codes and the
requirements of the gas supplier.
Dégagement conforme aux codes
d'installa tion locaux et aux exigences du
foumisseunde gaz.
Use only approved vent components (see
Approved Vent Components on Page 2).
These fireplaces must be vented
directly to the outside.
The vent system may not service multiple
appliances, and must never be connected to
a flue serving a separate solid fuel burning
appliance. The vent pipe is tested to be run
inside an enclosed wall (such as a chase).
There is no requirement for inspection
openings in the enclosing wall at any of the
joints in the vent pipe.
Installation of Vent Restrictor
A vent restrictor may be needed with this
appliance, install vent restrictor (provided)
in the appliance top flue outlet as shown
in Figure 17 (MPDT33, MPD35, MPD40
and MPD45) or rear flue outlet as shown in
Figure 18 (MPD35, MPD40 and MPD45). It
is held in place by friction, only.
Note: The vent restrictor is included in the
rebox.
(OUTSIDE UNIT)
CABINET TOP
FIREBOX TOP
VENT
COVER PLATE
(INSIDE UNIT)
CROSS SECTION
Figure 15: Top vent seal and cover plate
removal—MPD35/-40/-45 series models
(combined top and rear vent units)
COVER PLATE
SECURING SCREWS
(INSIDE UNIT)
CROSS SECTION
Figure 16: Rear vent seal and cover plate
removal—MPD35/-40/-45 series models
(combined top and rear vent units)
GASKET
TOP VENT
REAR VENT
KNOCKOUT
COVER PLATE
SECURING SCREWS
CAP AND
GASKET
KNOCKOUT
CABINET BACK
(OUTSIDE UNIT)
Select Venting System—Horizontal or
Vertical
With the appliance secured in framing,
determine vent routing and identify the
exterior termination location. The following
sections describe vertical (roof) and horizontal
(exterior wall) vent applications. Refer to the
section relating to your installation. A list of
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
lanimoN
T
T
VERTICAL TERMINATION SYSTEMS (ROOF)
See Figure 19 and Figures 30 through
32 on Page 17 and their associated
Vertical Vent Tables, which illustrate the
various vertical venting configurations that
are possible for use with these appliances.
Secure Vent® pipe applications are shown in
these Figures; Secure Flex® pipe may also be
used. A Vertical Vent Table summarizes each
system’s minimum and maximum vertical
and horizontal length values that can be used
to design and install the vent components in
a variety of applications.
Both these vertical vent systems terminate
through the roof. The minimum vent height
above the roof and/or adjacent walls is
specified in ANSI Z223.1-2009 (In Canada,
the current CAN/CSA-B149.1 installation
code) by major building codes. Always
consult your local codes for specific
requirements. A general guide to follow is the
Gas Vent Rule (refer to Figure 5 on Page 6).
Vertical (Straight) Installation
(Figure 19)
Determine the number of straight vent
sections required. 4 1/2 in. (114 mm),
10 1/2 in. (267 mm), 22 1/2 in. (572 mm),
34 1/2 in. (876 mm) and 46 1/2 in. (1181
mm) net section lengths are available (see
Tables on this page and Pages 35 and 36—Vent Sections). Plan the vent lengths so that
a joint does not occur at the intersection
of ceiling or roof joists. Refer to the Vent
Section Length Chart.
SV4.5CGV-1
Termination
Max. 40 ft
(12.2 m)
SV4.5FA or
SV4.5FB Flashing
AND SV4.5SC
Storm Collar
1 in (25.4 mm)
Minimum
Clearance to
Combustibles
SV4.5VF
Firestop/Spacer*
*When using Secure Flex,
use Firestop/Spacer
SF4.5VF.
SV4.5L6/12/24/36/48
Vent Sections
htgneLnoitceS
621426384
)sehcni(
noitceSteN
2/1-42/1-012/1-222/1-432/1-64
)sehcni(htgneL
tneVfothgieHsnoitceStneVforebmuN
sehcnitf
5.4573.0100001
957.0200002
5.01578.0010001
5152.1110002
5.91526.12100
1257.1020002
5.22578.1001001
5.52521.2120003
5.13526.2030003
5.43578.2000101
5.73521.3111003
5.34526.3021003
5457.3002002
5.64578.3000011
5.94521.4102003
1552.4100012
5.55526.4012003
7557.4001102
6652.5022004
5.76526.5003003
9657.5000202
276103004
5.37521.6100203
5.97526.6010203
1857.6000112
095.7021014
5.19526.7002013
3957.7000022
698101204
5.79521.8100023
2015.8200024
5.301526.8000303
8019
4115.9020024
71157.9105006
5.811578.9110305
6215.01001304
5.031578.01101305
53152.11006006
8315.11000404
5.931526.11000033
5.241578.11100405
100304
Table 7: Vent Section Length
Note: Convert inches into metric equivalent
measurement, as follows:
Millimeters (mm) = Inches x 25.4
Centimeters (cm) = Inches x 2.54
Meters (M) = Inches x .0254
SV4.5L64 1/2 in.
SV4.5L1210 1/2 in.
SV4.5L2422 1/2 in.
SV4.5L3634 1/2 in.
SV4.5L4846 1/2 in.
Table 8: Effective Vent Length
14
Figure 19
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Page 15
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
(Plumber's tape
Vertical (Offset) Installation
Analyze the vent routing and determine the
quantities of vent sections and number of
elbows required. Refer to Vertical Vent Figures and Tables on Page 14 to select
the type of vertical installation desired.
Vent sections are available in net lengths of
4 1/2 in. (114 mm), 10 1/2 in. (267 mm),
22 1/2 in. (572 mm), 34 1/2 in. (876 mm)
and 46 1/2 in. (1181 mm). Refer to the Vent Section Length Chart on Page 14 for an aid
in selecting length combinations. Elbows are
available in 90° and 45° configurations. Refer
to Figure 23 for the SV4.5E45 and SV4.5E90
elbow dimensional specifications.
Where required, a telescopic vent section (SV4.5LA) may be used to provide the
installer with an option in installing in tight
and confined spaces or where the vent run
made up of fixed length pieces develops a
joint in a undesirable location, or will not
build up to the required length. The SV4.5LA
Telescopic Vent Section has an effective
length of from 1 1/2 in. (38 mm) to 7 1/2 in.
(191 mm). The SV4.5LA is fitted with a
locking inclined channel end (identical to a
normal vent section component) and a plain
end with 3 pilot holes. Slip the plain end over
the locking channel end of a standard SV4.5
vent component the required distance and
secure with three screws.
Maintain a minimum 1 in. (25 mm)
clearance to combustible materials for
all vertical elements. Clearances for all
horizontal elements are 3 in. (76 mm)
on top, 1 in. (25 mm) on sides and 1 in.
(25 mm) on the bottom.
A. Frame ceiling opening—Use a plumb line
from the ceiling above the appliance to locate
center of the vertical run. Cut and/or frame
an opening, 10 1/2 in. x 10 1/2 in. (267 mm
x 267 mm) inside dimensions, about this
center mark (Figure 20).
B. Attach vent components to appliance—
Secure Vent® SV4.5 direct vent system
components are unitized concentric pipe
components featuring positive twist lock
connections (see Figure 18). All of the
appliances covered in this document are
fitted with collars having locking inclined
channels.
Min. 10-1/2"
(267 mm)
Min. 10-1/2"
(267 mm)
Figure 20
The dimpled end of the vent components
fit over the appliance collar to create the
positive twist lock connection.To attach a
vent component to the appliance collar, align
the dimpled end over the collar, adjusting
the radial alignment until the four locking
dimples are aligned with the inlet of the
four inclined channels on the collar (refer to Figure 21). Push the vent component
against the collar until it fully engages, then
twist the component clockwise, running the
dimples down and along the incline channels
until they seat at the end of the channels.
The unitized design of the Secure Vent®
components will engage and seal both the
inner and outer pipe without the need for
sealant or screws. If desired a #6 x 1/2 in.
screw may be used at the joint, but it is not
required as the pipe will securely lock when
twisted.
Note: An elbow may also be attached to the
appliance collar. Attach in the same manner
as you would a vent section.
C. Attach vent components to each other—
Other vent sections may be added to the
previously installed section in accordance
with the requirements of the vertical vent
figures and tables. To add another vent
component to a length of vent run, align the
dimpled end over the inclined channel end
of the previously installed section, adjusting
the radial alignment until the four locking
dimples are aligned with the inlets of the four
incline channels of the previous section.
Push the vent component against the
previous section until it fully engages, then
twist the component clockwise running the
dimples down and along the incline channels
until they seat at the end of the channels.
This seating position is indicated by the
alignment of the arrow and dimple as
shown in Figure 21.
D. Install firestop/spacer at ceiling—
When using Secure Vent, use SV4.5VF
firestop/spacer at ceiling joists; when using
Secure Flex®, use SF4.5VF firestop/spacer. If
there is living space above the ceiling level,
the firestop/spacer must be installed on the
bottom side of the ceiling. If attic space is
above the ceiling, the firestop/spacer must
be installed on the top side of the joist. Route
the vent sections through the framed opening
and secure the firestop/spacer with 8d nails
or other appropriate fasteners at each corner.
Remember to maintain 1 in. (25 mm)
clearance to combustibles, framing
members, and attic or ceiling insulation
when running vertical chimney sections.
Attic insulation shield (96K94) may be used
to obtain the required clearances indicated
here. See installation accessories table on
Pages 35 and 36. The gap between the vent
pipe and a vertical firestop can be sealed
with non-combustible caulking.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
E.Support the vertical vent run sections—
Note: Proper venting support is very
important.
Support the vertical portion of the venting
system every 8 feet (2.4m) above the
fireplace vent outlet. One method of support
is by utilizing field provided support straps
(conventional plumber's tape). Secure the
plumber's tape to the framing members
with nails or screws. Loop the tape around
the vent, securing the ends of the tape to
the framing. If desired, sheet metal screws
#6 x 1/2 in. length may be used to secure
the support straps to the vent pipe. See
Figure 22.
Align the dimple (four places) of
the upper vent section with the
opening of the locking incline
channel on the lower vent section or appliance collar. Twist
vent component clockwise to
engage and seal until arrow and
Arrow
Appliance Collar or
Vent Section
dimple align.
Dimple
Locking
Incline
Channel
Connected Vent
Sections
Arrow
Figure 21
Blocking
Support Straps
8 feet (2.4 m)
Maximum
1/2 inch (12.7
mm) minimum
clearance to
combustibles
Figure 22
)
15
Page 16
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
SV4.5E90
(90
°
Elbow)
8-1/8"
(206 mm)
Swivel Joint
(360
°
swivel)
4-13/16"
(122 mm)
SV4 .5E45
(45
°
El bow)
Swivel Joint
(360
°
swivel)
C
D
Storm
Collar
F. Change vent direction to horizontal/
inclined run—At transition from or to a
horizontal/inclined run, install the SV4.5E45
and SV4.5E90 elbows in the same manner as
the straight vent sections. The elbows feature
a twist section to allow them to be routed
about the center axis of their initial collar
section to align with the required direction
of the next vent run element. Twist elbow
sections in a clockwise direction only so as
to avoid the possiblity of unlocking any of
the previously connected vent sections. See
Figure 23.
Figure 23
G. Continue installation of horizontal/
inclined sections—Continue with the
installation of the straight vent sections
in horizontal/inclined run as described in
Step C. Install support straps every 5 ft
(1.52 m) along horizontal/inclined vent runs
using conventional plumber’s tape.
It is very important that the horizontal/
inclined run be maintained in a straight
(no dips), slightly elevated plane. The
recommended incline is approximately
1/4 in. per foot (20 mm per meter)
horizontal, in a direction away from the
fireplace. The rise per foot run ratios that
are smaller are acceptable all the way down
to at or near level. Use a carpenter’s level to
measure from a constant surface and adjust
the support straps as necessary.
It is important to maintain the required
clearances to combustibles: 1 in. (25 mm)
at all sides for all vertical runs; and 3 in.
(76 mm) at the top, 1 in. (25 mm) at sides,
and 1 in. (25 mm) at the bottom for all
horizontal/inclined runs.
H. Frame roof opening—Identify location for
vent at the roof. Cut and/or frame opening
per Roof Framing Chart and Figure 24.
Framing Dimensions for Roof
Pitch C D
0/12 10 1/2 in. 10 1/2 in.
(267 mm) (267 mm)
6/1210 1/2 in. 12 in.
(267 mm) (305 mm)
12/1210 1/2 in. 17 3/4 in.
(267 mm) (451 mm)
Figure 24
I.Install the roof flashing—Extend the vent
sections through the roof structure. Install
the roof flashing over the vent section and
position such that the vent column rises
vertically (use carpenters level) (Figure 25 ).
Nail along perimeter to secure flashing or
adjust roofing to overlap the flashing edges at
top and sides only and trim where necessary.
Seal the top and both sides of the flashing
with waterproof caulking.
J. Install the storm collar—Install the storm
collar, supplied with the flashing, over the
vent/flashing joint. See Figure 25. Loosen
the storm collar screw. Slide collar down
until it meets the top of the flashing. Tighten
the adjusting screw. Apply non-combustible
caulking or mastic around the circumference
of the joint to provide a water tight seal.
K. Install the vertical termination—The
final step involves installation of the
SV4.5CGV-1 Vertical Termination. Extend
the vent sections to the height as shown in
the "Vertical vent termination section" on
Page 5. The SV4.5CGV-1 Vertical Termination
(Figure 26) installs in the exact same fashion
as any other Secure Vent® section. Align the
termination over the end of the previously
installed section, adjusting the radial
alignment until the four locking dimples of
the termination are aligned with the inlets
of the four incline channels of the last vent
section. Push the termination down until
it fully engages, then twist the termination
clockwise running the dimples down and
along the incline channels until they seat at
the end of the channels.
Figure 26
If the vent system extends more than 5' (1.5
m) above the roof flashing, stabilizers may be
necessary. Additional screws may be used at
section joints for added stability. Guide wires
may be attached to the joint for additional
support on multiple joint configurations.
16
Figure 25
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Page 17
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
SF4.5VF.
VERTICAL VENT FIGURES/TABLES
Note:Secure Vent® (rigid vent pipe) is
shown in the figures; Secure Flex® (flexible
vent pipe) may also be used.
Note: It is very important that the horizontal/
inclined run be maintained in a straight
(no dips), slightly elevated plane. The
recommended incline is approximately 1/4 in.
per foot (20 mm per meter) horizontal, in a
direction away from the fireplace. The rise per
foot run ratios that are smaller are acceptable
all the way down to at or near level.
Note: SV4.5VF (Secure Vent), SF4.5VF
(Secure Flex®) firestop/spacer must be
used anytime vent pipe passes through
a combustible floor or ceiling. SV4.5HF
(Secure Vent), SF4.5HF (Secure Flex®)
firestop/spacer must be used anytime vent
pipe passes through a combustible wall.
Note: Two 45 degree elbows may be used in
place of one 90 degree elbow. The same rise
to run ratios, as shown in the venting figures
for 90 elbows, must be followed if 45 degree
elbows are used.
Note: An elbow is acceptable as 1 foot of
vertical rise, except where an elbow is the
only vertical component in the system. (See
Figure 36 on Page 21).
Ceiling
Firestop/
Spacer
SV4.5VF*
Max. 40 ft
(12.2 m)
*When using
Secure Flex, use
Ceiling Firestop/
Spacer SF4.5VF.
TABLE A
H MaximumV Minimum
(meters)
feetfeet
(meters)
2(0.610)1(0.305)
4(1.219)2(0.610)
6(1.829)3(0.914)
V
8(2.438)4(1.219)
V + H = 40 feet (12.2 meters) Max.
H = 8 feet (2.4 meters) Max.
Ratio V to H ratio is 1:2
This table shows a 1 (V) to 2 (H) ratio.
For every 1 foot of (V) vertical, you are
allowed 2 feet of (H) horizontal run, up
to a maximum horizontal run of 8 feet.
Example: If 8 feet of (H) horizontal
vent run is needed, then 4 feet
minimum (V) vertical vent will
be required.
Figure 28: Rear Vent—ONE 90-DEGREE ELBOW
H
Ceiling
Firestop/Spacer
SV4.5VF*
Wall
Firestop/Spacer
V1
*When using Secure Flex, use Ceiling Firestop/Spacer SF4.5VF.
**When using Secure Flex, use Wall Firestop/Spacer SF4.5HF.
SV4.5HF**
V
Figure 29: Top Vent—TWO 90-DEGREE ELBOWS
Ceiling
Firestop/Spacer
SV4.5VF*
*When using Secure Flex, use
Ceiling Firestop/Spacer
H
Note: Install the U-shaped vent restrictor in
any vent run with more than 8 ft of vertical
rise (See Page 13).
TABLE B
H Maximum
feet
(meters)
(1.524)
5
(1.524)
5
(3.048)
10
(4.572)
15
(6.096)
20
V + V1+ H = 40 feet (12.2 m) Max.
H = 20 feet (6.096 meters) Max.
V Minimum
feet
Elbow Only
1
2
3
4
(meters)
(0.305)
(0.610)
(0.914)
(1.219)
Example: If 20 feet of (H) horizontal vent
run is needed, then 4 feet minimum of
(V) vertical vent will be required.
This table shows a 1 (V) to 5 (H) ratio.
For every 1 foot of (V) vertical, you are
allowed 5 feet of (H) horizontal run, up to
a maximum horizontal run of 20 feet.
An elbow is acceptable as 1 foot of
vertical rise except where an elbow is the
only vertical component in the system.
See Figure 36.
Note: Install the U-shaped vent restrictor
in any vent run with more than 8 ft of
vertical rise (See Page 13).
A Vent Restrictor, as shown in
Figure 17 on Page 13, must be used in
this application.
Figure 27: Top Vent—STRAIGHT
WARNING
Under no circumstances, may separate sections of concentric flexible vent
pipe be joined together.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
17
Page 18
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
VERTICAL VENT FIGURES/TABLES
(continued)
TABLE C
+H
MaximumH MaximumV Minimum
H
1
2
4
6
8
(meters)
(0.610)
(1.219)
(1.829)
(2.438)
(meters)
feetfeetfeet
(1.524)
5
(3.048)
10
(4.572)
15
(6.096)
20
V + V1+ H + H1 = 40 feet (12.2 m) Max
H = 8 feet (2.438 meters) Max.
H + H1= 20 feet (6.096 meters) Max.
1
2
3
4
(meters)
(0.305)
(0.610)
(0.914)
(1.219)
Example: If 20 feet of (H) horizontal vent run is needed,
then 4 feet minimum of (V) vertical vent will be required.
This table shows a 1 (V) to 5 (H) ratio. For every 1 foot of
(V) vertical, you are allowed 5 feet of (H) horizontal run,
up to a maximum horizontal run of 20 feet.
Note: Install the U-shaped vent restrictor in any vent run
with more than 8 ft of vertical rise (See Page 13).
Figure 30: Rear Vent—THREE ELBOWS
V1
H1
Ceiling
Firestop/Spacer
SV4.5VF*
Wall
Firestop/Spacer
SV4.5HF**
V
*When using Secure Flex, use Ceiling Firestop/Spacer SF4.5VF.
**When using Secure Flex, use Wall Firestop/Spacer SF4.5HF.
Ceiling
Firestop/Spacer
SV4.5VF*
H
TABLE D
H
Maximum
H +
1
feetfeet
5
5
10
15
20
(meters)(meters)
(1.524)Elbow Only
(1.524)
(3.048)
(4.572)
(6.096)
H + H1 = 20 feet (6.096 m) Max.
+ H + H1 = 40 ft. (12.192 m) Max.
V + V
1
V Minimum
1
2
3
4
(0.305)
(0.610)
(0.914)
(1.219)
Example: If 20 feet of (H) horizontal vent run is needed, then 4
feet minimum of (V) vertical vent will be required.
This table shows a 1 (V) to 5 (H) ratio. For every 1 foot of (V)
vertical, you are allowed 5 feet of (H) horizontal run, up to a
maximum horizontal run of 20 feet.
An elbow is acceptable as 1 foot of vertical rise except where
an elbow is the only vertical component in the system. See
Figure 36.
Note: Install the U-shaped vent restrictor in any vent run with
more than 8 ft of vertical rise (See Page 13).
Ceiling
V
1
Firestop/Spacer
SV4.5VF*
Wall
Firestop/Spacer
SV4.5HF**
H
H
1
V
*When using Secure Flex, use Ceiling Firestop/Spacer SF4.5VF.
**When using Secure Flex, use Wall Firestop/Spacer SF4.5HF.
18
Figure 31: Top Vent—THREE ELBOWS
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Page 19
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
TYPICAL HORIZONTAL VENT INSTALLATION
HORIZONTAL (OUTSIDE WALL)
TERMINATION SYSTEM
Figure 33, and Figures 39 to 44 on
Pages 21 to 23 and their associated
Horizontal Vent Table illustrate the various
horizontal venting configurations that are
possible for use with these appliances.
Secure Vent® pipe applications are shown in
these figures; Secure Flex® pipe may also be
used. A Horizontal Vent Table summarizes
each system’s minimum and maximum
vertical and horizontal length values that
can be used to design and install the vent
components in a variety of applications. Both
of these horizontal vent systems terminate
through an outside wall. Building Codes limit
or prohibit terminating in specific areas.
Refer to Figure 8on Page 7 for location
guidelines.
Secure Vent SV4.5 direct vent system
components are unitized concentric pipe
components featuring positive twist lock
connection, (refer to Figure 21 on Page 15).
All of the appliances covered in this document
are fitted with collars having locking inclined
channels. The dimpled end of the vent
components fit over the appliance collar to
create the positive twist lock connection.
A.Plan the vent run—Analyze the vent
routing and determine the types and quantities
of sections required 4 1/2 in. (114 mm),
10 1/2 in. (267 mm), 22 1/2 in. (572 mm),
34 1/2 in. (876 mm) and 46 1/2 in. (1181 mm)
net section lengths are available. It is
recommended that you plan the venting so
that a joint does not occur in the ceiling or roof
joists. Allow for elbows as indicated in Figure 23
on Page 16.
Maintain a minimum 1 in. (25 mm) clearance
to combustibles on the vertical sections.
Clearances for the horizontal runs are; 3 in.
(76 mm) on top, 1 in. (25 mm) on sides, and
1 in. (25 mm) at the bottom.
B. Frame exterior wall opening—Locate
the center of the vent outlet on the exterior
wall according to the dimensions shown in
Figure 9 on Page 8. Cut and/or frame an
opening, 10 1/2 in. x 12 1/8 in. (267 mm
x 308 mm) inside dimensions, about this
center.
C.Frame ceiling opening—If the
vertical route is to penetrate a ceiling, use
plumb line to locate the center above the
appliance. Cut and/or frame an opening,
10 1/2 in. x 10 1/2 in. (267 mm x 267 mm)
inside dimensions, about this center (refer to
Figure 20 on Page 15).
D. Attach vent components to appliance—To
attach a vent component to the appliance
collar, align the dimpled end over the collar,
adjusting the radial alignment until the four
locking dimples are aligned with the inlets of
the four incline channels on the collar (refer to Figure 21on Page 15).
Building
Support
Framing
SV4.5E90
Elbow
ertical
V
Rise
Support
Brackets
Ceiling
Firestop/Spacer
Horizontal / Inclined Run
See Figure 24 on Page 15 for
vertical vent section support.
Fireplace
Figure 32: Typical Horizontal Vent Installation
Push the vent component against the
collar until it fully engages, then twist the
component clockwise, running the dimples
down and along the incline channels until they
seat at the end of the channels. The unitized
design of the Secure Vent components will
engage and seal both the inner and outer pipe
elements with the same procedure. Sealant
and securing screws are not required.
Note: An elbow may also be attached to the
appliance collar. Attach in the same manner
as you would a vent section.
E. Attach vent components to each other—
Other vent sections may be added to the
previously installed section in accordance
with the requirements of the vent tables.
To add another vent component to a length
of vent run, align the dimpled end of the
component over the inclined channel end of
the previously installed section, adjusting
the radial alignment until the four locking
dimples are aligned with the inlets of the four
incline channels of the previous section. Push
the vent component against the previous
section until it fully engages, then twist the
component clockwise running the dimples
down and along the incline channels until they
seat at the end of the channels.This seating
position is indicated by the alignment of the
arrow and dimple as shown in Figure 21 on
Page 15.
F.Install firestop/spacer at ceiling—
When using Secure Vent, use SV4.5VF
firestop/spacer at ceiling joists; when using
Secure Flex®, use SF4.5VF firestop/spacer. If
there is living space above the ceiling level,
the firestop/ spacer must be installed on the
bottom side of the ceiling. If attic space is
above the ceiling, the firestop/ spacer must
be installed on the top side of the joist. Route
the vent sections through the framed opening
and secure the firestop/spacer with 8d nails
or other appropriate fasteners at each corner.
Remember to maintain 1 in. (25 mm)
clearance to combustibles, framing
members, and attic or ceiling insulation
when running vertical chimney sections.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
SV4.5HT-2
Termination
SV4.5L6/12/24/36/48
Vent Sections
Support bracket spacing
every 5 ft (1.52 m)
Exterior
Wall
SV4.5HT-2
Termination
Exterior
Wall
G.Support the vertical run sections—
On the vertical run, support the venting
system every 8 feet (2.4m) above the
fireplace vent outlet with field provided
support straps (Plumber's tape). Attach the
straps to the vent pipe and secure to the
framing members with nails or screws. See
Figure 22 on Page 15.
H. Change vent direction—At transition
from or to a horizontal/inclined run, install
the SV4.5E45 and SV4.5E90 elbows in the
same manner as the straight vent sections.
The elbows feature a twist section to allow
them to be routed about the center axis
of their initial collar section to align with
the required direction of the next vent
run element. Twist elbow sections in a
clockwise direction only so as to avoid
the possiblity of unlocking any of the
previously connected vent sections. See Figure 23 on Page 16.
I. Continue installation of horizontal/
inclined sections—Continue with the
installation of the straight vent sections in
horizontal/inclined run as described in Step E. Install support straps every 5 ft. (1.52 m)
along horizontal/inclined vent runs using
conventional plumber’s tape. See Figure 32,
It is very important that the horizontal/
inclined run be maintained in a straight
(no dips), slightly elevated plane. The
recommended incline is approximately
1/4 in. per foot (20 mm per meter)
horizontal, in a direction away from the
fireplace. The rise per foot run ratios that
are smaller are acceptable all the way down
to at or near level. Use a carpenter’s level to
measure from a constant surface and adjust
the support straps as necessary.
It is important to maintain the required
clearances to combustibles: 1 in. (25 mm)
at all sides for all vertical runs; and 3 in.
(76 mm) at the top, 1 in. (25 mm) at sides,
and 1 in. (25 mm) at the bottom for all
horizontal/inclined runs.
19
Page 20
J. Assemble vent run to exterior wall—If
Siding
Stucco
1-1 /4 " Ma ximum Recess of
the Square Termination into
Exterio r Finishing Mater ia l
Exterior Surface of
Framing
6 in. to 9-1/4 in.
(152 to 235 mm)**
Exterior Surface of Siding
Interior Surface of
Finished Wall
Maximum wall thickness
10 in.(254 mm)**
SV4.5HT-2
Square Termination
Ma xim um Ex ten t o f
Ve nt R un S ecti o n s
Rela tiv e to E xteri or
Su rfa ce of F ram ing
Last Vent Section. Use
T e le s co p ic V en t
Section (SV4.5LA), If
Necessary
Adapter
SV4.5RCH
SV4.5HT-2
Square Termination
*Use silicone caulking to seal
the t op and s ides o f the
termination, u p to t he
unde rlaym ent , s tuc co , or
mas o n r y w a l l s u r fa c e .
**For thicknesses greater
than 10 inches, see Table 8.
*Caulk
*Caulk
SV4.5HT-2
Termination
10-1/2 in.
(267mm)
7 in.
(178)
5-1/8 in.
(130 mm)
12-1/8 in.
(308 mm)
Note: Centerline of Vent Piping is
NOT the Same as the Centerline of
the Framed Opening.
6 to 48 in. Vent Section,
Telescopic vent section,
Elbow or Appliance Collar
See Figure 13 on Page 11
for Min. Distance to Base
of Appliance.
Base of Appliance
3 in.
(76 mm)
1 in.
(25.4 mm)
Adapter
SV4.5RCH
To help minimize water
infiltration it is recommended that
the Firestop/Spacer (SV4.5HF)
be installed on the exterior
side of the wall.
not previously measured, locate the center
of the vent at the exterior wall. Prepare an
opening as described in Step B. Assemble
the vent system to point where the terminus
of the last section is within 7 in. (178 mm) to
11 1/4 in. (286 mm) inboard of the exterior
surface to which the SV4.5 HT termination is
to be attached, see Figure 34. If the terminus
of the last section is not within this distance,
use the telescopic vent section SV4.5LA,
as the last vent section. For wall thicknesses
greater than that shown in Figure 34, refer
to Table 9 on Page 21. This table lists the
additional venting components needed (in
addition to the termination and adaptor) for a
particular range of wall thicknesses.
K.Attach termination adaptor—Attach
the adaptor (SV4.5RCH, provided with
the termination) to the vent section or
telescoping vent section), elbow or appliance
collar as shown in Figure 33 in the same
manner as any SV4.5 vent component (refer
to Step E).
L.Install Firestop/Spacer at exterior wall—
When using the square termination, install
SV4.5HF (Secure Vent®), SF4.5HF (Secure
Flex®) Firestop/Spacer over the opening at
the exterior side of the framing, long side up,
with the 3 inch spacer clearance at the top as
shown in Figure 33, and nail into place (the
Firestop/Spacer may also be installed over the
opening at the interior side of the framing).
M. Install the desired termination
1. Install the square termination
(SV4.5HT-2 or SV4.5HTSS)—For the last
step , from outside the exterior wall, slide
the collars of the termination onto the
adaptor (the outer over the outer and the
inner inside the inner) until the termination
seats against the exterior wall surface to
which it will be attached. Orient the housing
of the termination with the arrow pointed
upwards. Secure the termination to the
exterior wall. The horizontal termination
must not be recessed into the exterior wall
or siding by more than the 1 1/4 in. (32 mm)
as shown in Figure 34.
SVHRK Snorkel Cap—The snorkel cap
is designed to be fitted into a basement
window box. The SVHRK cap is for use with
flex vent. The vertical distance between
the inlet and outlet of the cap is 28 in.
(711 mm).
IMPORTANT: The vent termination
is hot while in operation and for a
period of time following the use of the
fireplace. To prevent contact with hot
surfaces, we recommend the use of a
Termination Guard. See Page 36. This
can be purchased at your local dealer.
20
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Figure 33: Installing the Square Horizontal Termination (SV4.5HT-2)
Figure 34: Venting Connection and Exterior Wall Recessing of the Horizontal
Square Termination (SV4.5HT-2)
Horizontal terminations have been designed to perform in a wide range of weather
conditions. Our terminations meet or exceed industry standards.
When selecting the locations of your horizontal terminations, do not place the
termination where water from eaves and adjoining rooflines may create a heavy flow
of cascading water onto the termination cap. If the cap must be placed where the
possibility of cascading water exists, it is the responsibility of the builder to direct the
water away from the termination cap by using gutters or other means.
Take care to carefully follow the installation instructions for the termination, including
the use of silicone caulking where required.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Page 21
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
HORIZONTAL VENT FIGURES/TABLES
Note:Secure Vent® components (rigid vent pipe and terminal) are
shown in the figures; Secure Flex® components (flexible vent pipe and
terminal) may also be used.
Note: Two 45 degree elbows may be used in place of one 90 degree
elbow. The same rise to run ratios, as shown in the venting figures for
90 elbows, must be followed if 45 degree elbows are used.
Note: It is very important that the horizontal/inclined run be
maintained in a straight (no dips), slightly elevated plane. The
recommended incline is approximately 1/4 in. per foot (20 mm per
meter) horizontal, in a direction away from the replace. The rise
per foot run ratios that are smaller are acceptable all the way down to
at or near level.
Note: SV4.5VF (Secure Vent®), SF4.5VF (Secure Flex) firestop/spacer
must be used anytime vent pipe passes through a combustible floor or
ceiling. SV4.5HF (Secure Vent), SF4.5HF (Secure Flex) firestop/spacer
must be used anytime vent pipe passes through a combustible wall.
WARNING
Under no circumstances, may separate sections of
concentric flexible vent pipe be joined together.
Venting Components Required for Various Exterior Wall Thick-
Termination Kit Only6–9 1/4 (152–235)
Termination Kit and 6 in.
Vent Section (SV4.5L6)
Termination Kit and 12 in.
Vent Section (SV4.5L12)
Termination Kit and
Telescopic Section
(SV4.5L12)
Table 9
Note: See Figure 34 showing wall thickness range
when using SV4.5HT-2 termination kit.
10 3/4–14 (2733–356)
16 3/4–20 (426–508)
11 3/4–20 (299–508)
TABLE F
H MaximumV Minimum
(meters)
feet
(0.914)
3
**When using SecureFlex, use Wall Firestop/
Spacer SF4.5HF.
Square termination (SV4.5HT-2) shown.
See Table 9 as an aid in venting component selection for a particular range of
exterior wall thicknesses.
(meters)
feet
Elbow Only
Note: Install the U-shaped vent
restrictor in any vent run with
more than 8 ft of vertical rise
(See Page 13).
H
V
Wall Firestop/
Spacer
SV4.5HF**
Figure 36: Top Vent—ONE 90-DEGREE ELBOW—
ELBOW CONNECTION AT APPLIANCE
TABLE G
H Maximum
(meters)
feetfeet
(1.524)
5
V Minimum
(meters)
1(0.305)
10(3.048)2(0.610)
15(4.572)3(0.914)
20(6.096)4(1.219)
V + H = 40 feet (12.2 m) Max.
H = 20 ft. (6.096 m) Max.
H
Example: If 20 feet of (H)
horizontal vent run is needed,
then 4 feet minimum of (V)
vertical vent will be required.
This table shows a 1 (V) to 5
(H) ratio. For every 1 foot of
(V) vertical, you are allowed 5
feet of (H) horizontal run, up
to a maximum horizontal run
of 20 feet.
H = 28 in. (711 mm) Maximum.
H
Wall Firestop/
Spacer
7 in
(178 mm)
Only the square termination (SV4.5HT-2) may be used.
See Table 9 as an aid in venting component selection for a particular
range of exterior wall thicknesses.
SV4.5HF**
**When using Secure Flex, use Wall Firestop/Spacer SF4.5HF.
Figure 35: Rear Vent—NO ELBOWS
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
V
Ceiling
Wall Firestop/
Spacer SV4.5HF**
*When using Secure Flex, use Ceiling Firestop/Spacer SF4.5VF.
**When using Secure Flex, use Wall Firestop/Spacer SF4.5HF.
Square termination (SV4.5HT-2) shown.
See Table 9 as an aid in venting component selection for a particular range
of exterior wall thicknesses.
Firestop/
Spacer
SV4.5VF*
Note: Install the U-shaped vent restrictor in any vent run with more
than 8 ft of vertical rise (See Page 13).
Figure 37: Top Vent—ONE 90-DEGREE ELBOW—
ELBOW CONNECTION NOT DIRECTLY AT APPLIANCE
21
Page 22
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
HORIZONTAL VENT FIGURES/TABLES (continued)
H
H
1
Ceiling
Firestop/Spacer
SV4.5VF*
Wall Firestop/
Spacer
SV4.5HF**
V
*When using Secure Flex , use Ceiling Firestop/Spacer SF4.5VF.
**When using Secure Flex, use Wall Firestop/Spacer SF4.5HF.
Square termination (SV4.5HT-2) shown.
TABLE H
MaximumH Maximum
+H
H
1
(meters)
feet
(1.524)
5
(3.048)
10
(4.572)
15
(6.096)
20
V + H + H1 = 40 feet (12.2 m) Max.
H = 8 feet (2.438 meters) Max.
H + H1= 20 feet (6.096 meters) Max.
(meters)
feet
2(0.610)1(0.305)
4(1.219)2(0.610)
6(1.829)3(0.914)
8(2.438)4(1.219)
V Minimum
feet
(meters)
Example: If 20 feet of (H) horizontal vent run is needed, then 4
feet minimum of (V) vertical vent will be required.
This table shows a 1 (V) to 5 (H) ratio. For every 1 foot of (V)
vertical, you are allowed 5 feet of (H) horizontal run, up to a
maximum horizontal run of 20 feet.
®
See Table 9 on Page 21 as an aid in venting component
selection for a particular range of exterior wall thicknesses.
Note: Install the U-shaped vent restrictor in any vent run with
more than 8 ft of vertical rise (See Page 13).
Figure 38: Rear Vent—TWO 90-DEGREE ELBOWS
Wall Firestop/Spacer
SV4.5HF**
H
H
1
*When using Secure Flex, use Ceiling Firestop/Spacer SF4.5VF.
**When using Secure Flex, use Wall Firestop/Spacer SF4.5HF.
Wall Firestop/Spacer
SV4.5HF**
Ceiling Firestop/Spacer
SV4.5VF*
Square termination (SV4.5HT-2) shown.
See Table 9 on Page 21 as an aid in venting component selection for a particular range
of exterior wall thicknesses.
Note: Install the U-shaped vent restrictor in any vent run with more than 8 ft of vertical
rise (See Page 13).
Figure 39: Top Vent—TWO 90-DEGREE ELBOWS
TABLE J
+ H
H
Maximum
1
(meters)
feet
(0.914)Elbow Only
3
(1.524)
5
(3.048)
V
10
(4.572)
15
(6.096)
20
V +H+ H1 = 40 feet (12.2 m) Max.
+ H1 = 20 ft. (6.096 m) Max.
H
V Minimum
(meters)
feet
1(0.305)
2(0.610)
3(0.914)
4(1.219)
Example: If 20 feet of (H) horizontal vent run is
needed, then 4 feet minimum of (V) vertical vent
will be required.
This table shows a 1 (V) to 5 (H) ratio. For every
1 foot of (V) vertical, you are allowed 5 feet of (H)
horizontal run, up to a maximum horizontal run of
20 feet.
An elbow is acceptable as 1 foot of vertical
rise except where an elbow is the only vertical
component in the system. See Figure 36.
22
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Page 23
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
HORIZONTAL VENT FIGURES/TABLES (continued)
H
2
*When using Secure Flex , use Ceiling Firestop/Spacer SF4.5VF.
**When using Secure Flex, use Wall Firestop/Spacer SF4.5HF.
®
Square termination
(SV4.5HT-2) shown.
See Table 9 on Page 21 as
an aid in venting component
selection for a particular range
of exterior wall thicknesses.
Note: Install the U-shaped vent
restrictor in any vent run with
more than 8 ft of vertical rise
(See Page 13).
Wall Firestop/Spacer
SV4.5HF**
H
1
Ceiling
Firestop/Spacer
SV4.5VF*
V
TABLE K
+ H1+ H
H
feetfeetfeet
Maximum
2
(meters)
H Maximum
(meters)
V Minimum
(meters)
5(1.524)2(0.610)1(0.305)
10(3.048)4(1.219)2(0.610)
15
(4.572)
6(1.829)3(0.914)
20(6.096)8(2.438)4(1.219)
V + H + H1+ H2 = 40 feet (12.2 m) Max.
H = 8 feet (2.438 meters) Max.
H + H1+ H2= 20 feet (6.096 meters) Max.
Example: If 20 feet of (H) horizontal vent run
is needed, then 4 feet minimum of (V) vertical
vent will be required.
This table shows a 1 (V) to 5 (H) ratio. For
every 1 foot of (V) vertical, you are allowed 5
H
feet of (H) horizontal run, up to a maximum
horizontal run of 20 feet.
Figure 40: Rear Vent—THREE 90-DEGREE ELBOWS
*When using Secure Flex, use
Ceiling Firestop/Spacer SF4.5VF.
H
1
Wall Firestop/Spacer
SV4.5HF**
V
1
Square termination (SV4.5HT-2) shown.
**When using Secure Flex, use
Wall Firestop/Spacer SF4.5HF.
Ceiling
Firestop/Spacer
SV4.5VF*
H
Wall Firestop/Spacer
SV4.5HF**
See Table 9 on Page 21 as an aid in venting component selection for a particular range of
exterior wall thicknesses.
Note: Install the U-shaped vent restrictor in any vent run with more than 8 ft of vertical rise
(See Page 13).
Figure 41: Top Vent—THREE 90-DEGREE ELBOWS
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
TABLE L
H Maximum
(meters)
feet
(1.524)
5
(1.524)
5
10
15
20
Example: If 20 feet of (H) horizontal vent
V
(3.048)
(4.572)
(6.096)
+ H1 = 20 feet (6.096 m) Max.
H
+ V +H+ H = 40 ft. (12.192 m) Max.
V
11
V Minimum
feet
Elbow Only
1
2
3
4
run is needed, then 4 feet minimum of (V)
vertical vent will be required.
This table shows a 1 (V) to 5 (H) ratio.
For every 1 foot of (V) vertical, you are
allowed 5 feet of (H) horizontal run, up to a
maximum horizontal run of 20 feet.
An elbow is acceptable as 1 foot of vertical
rise except where an elbow is the only
vertical component in the system. See
Figure 36.
(meters)
(0.305)
(0.610)
(0.914)
(1.219)
23
Page 24
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
5 in. (127 mm)
Radius Minimum
Flexible Vent Section
GEAR
CLAMPS
Adaptor
(SV4.5RF)
Appl y ONLY MIL-PAC BLAC K HIGH
TEMPERATURE SEALANT (Catalog No.
10K81) to the outside surface of both
collars of the adaptor (be especially
careful to fill the grooves of the outer
collar to be covered by the flexible
pipe ) and slide flexib le pipe over
inn er and outer adapt or col lars.
NOTE: OUTER PIPE IS PULLED AWAY TO
SHOW THE DETAIL OF THE INNER PIPE
FLEX VENT
1-3/4 in. (44 mm)
Flexible Pipe and
Adaptor Outer
Collar Overlap
1-3/4 in. (44 mm)
Flexible Pipe and
Adaptor Inner
Collar Overlap
SECURING SCREW
(3 PLACES EQUALLY SPACED
JUST BELOW GEAR CLAMP)
Attach Adaptor to Appliance
Collar, or Secure Vent Sections
SECURING SCREW
(3 PLACES EQUALLY SPACED
JUST BELOW GEAR CLAMP)
VERTICAL OR HORIZONTAL VENTING USING
SECURE FLEX
Secure Flex® venting kits and components
may be used in any venting application
where rigid Secure Vent® (SV4.5) direct vent
components can be used. All restrictions,
clearances and allowances that pertain to
the rigid piping apply to the flexible venting.
Secure Flex kits may not be modified; also,
under no circumstances may separate
sections of flex pipe be joined together.
Secure Flex kits may be added to the end
of a vent run made up of rigid Secure Vent
(SV4.5) vent sections provided that doing so
does not violate any of the venting length,
height, routing, horizontal to vertical ratio
requirements or clearance considerations
detailed in this manual.
Secure Flex kits come with an included
adaptor that can be fitted to the appliance
collar or the inclined channel end of the last
Secure Vent (SV4.5) vent section in a rigid
system in the exact same fashion as any
other Secure Vent section. Align the dimpled
end of the adaptor over the previously
installed section or appliance collar, adjusting
the radial alignment until the four locking
dimples of the adaptor are aligned with the
inlets of the four incline channels of the last
vent section or collar. Push on the adaptor
until it fully engages, then twist the adaptor
clockwise running the dimples down and
along the incline channels until they seat at
the end of the channels.
Attach the flexible vent to the adaptor as
follows (see Figure 42):
A. Install the Inner Flex Pipe
1. Install the small gear clamp loosely around
the inner flexible vent pipe, push it back out
of the way.
2. Apply a bead of Mill-Pac Black (700°F)
high temperature sealant—Catalog
No. 10K81) to the inner adaptor collar,
approximately 1/2 inch from the end.
3. Pull and extend the inner flexible vent pipe.
4. Slide the inner flex pipe over the
adaptor collar. Ensure the flexible vent pipe
completely engages the adaptor collar to a
distance of 1 3/4 inches from the end, and
that it is free from damage or tears.
5. Slide the gear clamp down and tighten it
fully to secure the flexible vent to the adaptor
inner collar approximately 3/4 inch from the
end of the flex.
6. Install three screws 120 degrees apart
through the flexible vent pipe and into the
adaptor collar just below the gear clamp to
provide additional security to the connection.
B. Install the Outer Flex Pipe
1. Install the large gear clamp loosely around
the outer flexible vent pipe, push it back out
of the way.
24
®
KITS AND COMPONENTS
Figure 42
2. Apply a bead of Mill-Pac Black (700°F)
high temperature sealant—Catalog No.
10K81) to the outer adaptor collar; to
the grooves of the collar which extend
approximately 1 inch from the end and to the
flat surface, approximately 1 3/8 inches from
the end.
3. Pull and extend the outer flexible vent pipe.
4. Slide the outer flex pipe over the
adaptor collar. Ensure the flexible vent pipe
completely engages the adaptor collar to a
distance of 1 3/4 in. from the end, and that it
is free from damage or tears.
5. Slide the gear clamp down and tighten it
fully to secure the flexible vent to the adaptor
outer collar approximately 3/4 inch from the
end of the flex.
6. Install three screws 120 degrees apart
through the flexible vent pipe and into the
adaptor collar just below the gear clamp to
provide additional security to the connection.
C. Route Flex Vent
Ensure that the flex vent is properly routed to
provide the required clearance. Do Not allow
the flexible vent to bend in a radius tighter
than 5 in. (127 mm). Refer to Figure 43.
Place the internal flex vent spacers evenly
and avoid kinking the inner pipe. Support
horizontal sections of flex vent with metal
straps at 2 ft (0.61 m) intervals.
D. Install Firestop/Spacers at ceilings and walls
When Secure Flex penetrates a wall or
ceiling, a firestop/spacer is required: use the
SF4.5 VF firestop/spacer for ceilings and the
SF4.5 HF firestop/spacer for walls.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
See the appropriate sections and figures
shown throughout the venting section for
their installation requirments.
Figure 43
E. Attach Flex Vent to Termination
Secure Flex components can be purchased
separately and attached to bulk lengths
of Secure Flex flexible tubing cut to size
at the job site. Secure the flexible vent to
the Secure Flex terminations in the same
manner (see Figure 42) as it was attached
to the adaptor.
Note: Secure Flex vent must be attached
to Secure Flex terminations only. DO NOT
substitute Secure Vent terminations
or the Secure Vent adaptor for Secure
Flex components. The collars of Secure
Flex terminations and adaptors have a
different circumference than that used
with the Secure Vent pipe. Additionally,
Secure Flex components have an extended
length center tube for use in attaching the
flexible vent.
Page 25
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
JUNCTION BOX
Step 5. FIELD WIRING
CAUTION
The ground supply lead must be
connected to the wire attached to
the green ground screw located
on the outlet box (see wiring diagrams). Failure to do so
will result in a potential safety
hazard. The appliance must be
electrically grounded in accordance with local codes or, in
the absence of local codes, the
National Electrical Code, ANSI/
NFPA 70—latest edition (in
Canada, the current CSA C22-1
Canadian Electrical Code).
CAUTION: Label all wires prior to disconnection when servicing controls. Wiring
errors can cause improper and dangerous
operation.
ATTENTION: Au moment de l’entretien
des commandes, étiquetez tous les
fils avant de les débrancher. Des
erreurs de cáblage peuvent entraîner
un fonctionnement inadéquat et
dangereux.
Verify proper operation after servicing.
S’assurer que l’appareil fonctionne
adéquatement une fois l'entretien
terminé.
R
BATTERY HOLDER
AC/DC
POWER
ADAPTOR
Y
G
O
B
120V AC
HOT
NEUTRAL
GROUND
LIMIT SWITCH
B-VENT MODELS
ONLY
BL = BLUE
G = GREEN
O = ORANGE
W = WHITE
Y = YELLOW
SCHEMATIC REPRESENTATION ONLY
REMOTE RECEIVER
WIRING COLOR CODE
P/N 580491-01
B
W
G
OPTIONAL
ON/OFF SWITCH
WALL SWITCH
B = BLACK
BR = BROWN
GY = GRAY
PU = PURPLE
R = RED
WALL MOUNTED CONFIGURATION FOR FAN SWITCH (OPTIONAL)
(OPTIONAL)
BK/W(1)
FAN
THERMOPILE
TP-TH
TP
TH
JUNCTION BOX
GAS VALVE
Figure 45: Wiring Diagram—Millivolt
Gas Valves
ELECTRONIC PILOT ASSEMBLY
HOOD
PROFLAME VALVE
B
R
W
BL
PILOT TUBE
SPARK WIRE CABLE
PILOT GROUND WIRE
R
R
B
Y
Y
G
O
W
PROFLAME DFC BOARD
BL
B
G
B
OPTIONAL CPI SWITCH
OFF (O) = INTERMITTENT PILOT MODE
ON (-) = STANDING PILOT MODE
BLACK
BK
R
W
GR
IGNITER ROD
FLAME SENSOR
B
PILOT
SENSOR
CABLE
DFC WIRE HARNESS
Refer to Section A for millivolt appliances
and Section B for electronic appliances. The
gas valve is set in place and pre-wired at the
factory on both models.
A. Millivolt Wiring(see Figure 44)
Millivolt units are not provided with any
factory-installed controls; therefore, one
of the optional control switches is required
to operate the unit (ON/OFF Wall Switch,
Unit-Mountable ON/OFF Switch*, Thermostat,
Remote Control). See the fireplace Care and Operation Instructions for details.
[*If using a Unit-Mountable ON/OFF Rocker
Switch with an optional Style View Door, mount
the Rocker Switch on the door instead of the
unit.]
1. If installing an ON/OFF wall switch or
thermostat, mount it in a convenient
location on a wall near the fireplace.
2. Wire the control switch within the millivolt
AC
120 V
control circuit using the 15 feet of 2
conductor wire supplied with the unit.
Note: The supplied 15 feet of 2 conductor
wire has one end of each conductor
connected to the gas valve circuit and the
other end of each conductor placed loose
inside the bottom compartment.
CAUTION
In millivolt systems, do NOT connect
a Wall Switch to a 120V power supply.
B. Electronic Wiring(Figures 48 & 49)
One of the following optional controls
also may be used: ON/OFF Wall Switch,
Thermostat, Remote Control (see fireplace
Care and Operation Instructions for details.).
Note: Electronic models must be connected
to the main power supply.
1. Route a 3-wire 120Vac 60Hz 1ph power
supply to the appliance junction box.
2. Remove the electrical inlet cover plate
from the side of the unit by removing the
plate’s securing screws (see Figure 12,
Page 11).
3. Remove the cover plate knockout; then
feed the power supply wire through
the knockout opening and into the unit
junction box.
4. SeeFigures 48 & 49. Connect the black
power supply wire to the lower outlet’s
red pigtail lead.
Connect the white power supply wire to
the outlet’s common terminal.
5. Connect the ground supply wire to the
pigtail lead attached to the outlet’s green
ground screw.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
25
Page 26
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
BLOWER CONTROLCIRCUITWIRING
Receptacle
Receptacle
Note: Remote receiver should be located
in the wall, or if installed in the control
compartment, pulled all the way forward and
completely to the left or right against the
corner posts.
6. If wall-mounted ON/OFF control or
thermostat is to be used, mount it in a
convenient location on a wall near the
fireplace.
7. If an optional control is to be used, wire
it in the low voltage circuit as shown in
Figures 48 and 49.
Note: The supplied 15 feet of 2 conductor
wire has one end of each conductor
connected to the gas valve circuit and the
other end of each conductor placed loose
inside the bottom compartment.
8. After the wiring is complete, replace the
cover plate.
WARNING
Electronic models of these appliances are equipped with a threeprong (grounding) plug utilized
in connecting the electronic
components to the junction box
in the lower compartment. This
grounding plug provides protection against shock hazard and
should be plugged directly into
the properly grounded threeprong receptacle. DO NOT cut
or remove the grounding prong
from the plug.
Step 6.WIRING—OPTIONAL FORCED
AIR BLOWER KIT
FBK-100 and FBK-200 Kits
(See Figure 45 on Page 25)
An electrical outlet box is provided for
the installation of the FBK-100, FBK-200
forced air blower kits. Electrical power must
be provided to this box to operate these
blowers. Install the blower kits according to
the installation instructions provided with
the kits.
120V, 60HZ, 1PH
neerG - dnuorG
etihW - lar
t
ueN
Black
White
Green
Plug blower
into this
receptacle
Blower
Ground
Figure 46: Junction Box Wiring
FBK-250 Blower Kit
(See Figure 45 on Page 25)
An electrical outlet box is provided for the
installation of the FBK-250 forced air blower
kit. Electrical power must be provided to
this box to operate these blowers. Install
the blower kit according to the installation
instructions provided with the kit.
Note: The tab connecting the receptacles of
the outlet box must be broken in FBK-100
and FBK-200 blower kit applications. See
Figure 46.
* Wall-mounted
ON/ OFF Blower
Switch or Variable
Speed Control Switch.
120 VAC - Black
Junction Box
Tab Intact
Field Wired
Factory Wired
Tab
Broken
Red
Hot
Side of
Neutral
Side of
Green
Ground
Screw
Step 7. CONNECTING GAS LINE
Make gas line connections. All codes require
a shut-off valve mounted in the supply
line. Figure 47 illustrates two methods for
connecting the gas supply. The flex-line
method is acceptable in the U.S., however,
Canadian requirements vary depending on
locality. Installation must be in compliance
with local codes.
These appliances are equipped with a gas flex
line for use (where permitted) in connecting
the unit to the gas line. A gas flex line is
provided to aid in attaching the direct vent
appliance to the gas supply. The gas flex line
can only be used where local codes permit.
Refer to Figure 47 for flex line description.
The flex line is rated for both natural and
propane gas. A manual shut off valve is also
provided with the flex line.
The gas control valve is located in the lower
control compartment.
To access the valve open the lower control
compartment door (see Figure 48 ) by
pushing in the right top corner of the door.
(The door is hinged at the bottom.) Remove
the bottom compartment door by sliding
the hinge pin, located at the door’s left side,
to the right until it disengages from the left
corner post hole. Pull the door diagonally to
the left, away from the fireplace.
The millivolt control valve has a 3/8 in.
(10 mm) NPT thread inlet port. The electronic
control valve has a 1/2 in. (13 mm) NPT
thread inlet port and is fitted with a 1/2 in. x
3/8 in. (13 mm x 10 mm) NPT fitting.
Secure all joints tightly using appropriate
tools and sealing compounds (ensure
propane resistant compounds are used
in propane applications). Optional: Seal
around the gas line to prevent cold air
leakage. Gas line holes and other openings
can be caulked or stuffed with unfaced
fiberglass insulation.
All codes require a shut-off valve mounted
in the supply line. The orientation of
the shut-off valve should face the front.
Figure 47 illustrates two methods for
connecting the gas supply. A sediment Trap
is recommended to prevent moisture and
debris in the gas line for damaging the valve.
WARNING
Never use an open flame to
check for leaks.
26
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Page 27
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Thermocouple
HoodIgniter Rod
Thermopile
Pilot
Nozzels
3/8 in.
(9 mm)
Min
Gas
Stub
1/2" x 3/8" Flare
Shut-Off Valve
3/8" Flex Tubing
3/8" NPT x 3/8"
Flare Fitting
3/8" Nipple
3/8" Union
3/8" Close Nipple
3/8" Shut-Off Valve
1/2" x 3/8"
Reducer
Gas
Valve
Optional Gas Flex Line Connector
Figure 47: Gas Connection
Millivolt Appliance Checkout
The pilot flame should be steady, not lifting
or floating. Flame should be blue in color
with traces of orange at the outer edge.
The top 3/8 in. (10 mm) at the pilot generator
(thermopile) and the top 1/8 in. minimum
(tip) of the quick drop out thermocouple
should be engulfed in the pilot flame.
The flame should project 1 in. (25 mm)
beyond the hood at all three ports (see
Figure 49). Replace logs if removed for pilot
inspection.
To light the burner; turn “ON” the remote wall
switch and rotate the gas valve control knob
counterclockwise to the “ON” position (“ON”
will be at the top side of the valve).
TEST ALL CONNECTIONS FOR GAS LEAKS
(FACTORY AND FIELD)
Turn on gas supply and test for gas leaks,
using a gas leak test solution (also referred to
as bubble leak solution).
Note: Using a soapy water solution is an
effective leak test solution but it is not
recommended, because the soap residue
that is left on the pipes/fittings can result in
corrosion over time.
A. Light the appliance (refer to the
B. Brush all joints and connections with the
C. When the gas lines are tested and
Main Gas
Shut-Off Valve
Gas Valve
(Optional) Burner
ON/OFF Switch
Figure 48: Millivolt Gas Valve—Lower Control Compartment
Step 8. VERIFYING APPLIANCE
OPERATION
With gas line installed, run initial system
checkout before closing up the front of the
unit. Follow the pilot lighting instructions
provided in the Care and Operation Instructions. For piezo igniter location
on millivolt appliances, see Figure 44 on Page 25.
Note: Lighting Instructions are also found on
the literature tag tied to the gas piping next
lighting instructions label in the control
compartment or in the Care and Operation
Instructions manual).
gas leak test solution to check for leaks. If
bubbles are formed, or gas odor is detected,
turn the gas control knob (off/pilot/on) to
the “OFF” position (millivolt units), or turn
the receiver or remote control to the “OFF”
position (electronic units). Either tighten or
refasten the leaking connection, then retest
as described above.
leak free, be sure to rinse off the leak
testing solution.
to the gas valve. To access the tag, open the
lower control compartment door (Figure 48)
by pushing in simultaneously the left and
right top corners of the door (the door is
hinged at the bottom). Remove the bottom
compartment door by sliding the hinge
pin, located at the door’s left side, to the
right until it disengages from the left corner
post hole.
When first lighting the appliance, it will take
a few minutes for the line to purge itself of
air. Once purging is complete, the pilot and
burner will light and operate as indicated
in the instruction manual. Subsequent
lighting of the appliance will not require such
purging. Inspect the pilot flame (remove logs,
if necessary, handling carefully).
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Piezo
Door Latch
Figure 49: Millivolt Pilot
Electronic Appliance Checkout
To light the burner, turn ‘ON’ the wall or
remote control switch. Ensure the igniter
lights the pilot. The pilot flame should engulf
the flame rod as shown in Figure 50.
Ignitor
Igniter
Pilot
Pilot Hood
Hood
Flame Rod
Sensor
(sensor)
Figure 50: Electronic Pilot
27
Page 28
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Glowing Embers
Step 9. INSTALL VOLCANIC STONE,
GLOWING EMBERS AND LOGS
WARNING
•DONOTattempttoinstallthe
logs until the appliance installation has been completed, the gas
line connected and tested for leaks
and the initial burner operation
has been checked out.
• The size and position of the log set
was engineered to give the appliance a safe, reliable and attractive
flame pattern. Any attempt to use
a different log set in the fireplace
will void the warranty and will
result in incomplete combustion,
sooting, and poor flame quality.
• Logs get very hot and will remain
hot up to one hour after gas supply
is turned off. Handle only when
logs are cool. Turn off all electricity
to the appliance before you install
grate, volcanic stone, embers
and logs.
• This appliance is not designed to
burn wood. Any attempt to do so
could cause irreparable damage to
the appliance and prove hazardous
to your safety.
• If logs are not installed accord-
ing to the log installation instructions, flame impingement and
improper combustion could
occur and result in soot and/or
excessive production of carbon
monoxide (CO), a colorless,
odorless, toxic gas.
Figure 52
NOTE: Turn off all electricity to the appliance
before you install volcanic stone, embers
and logs.
Step 1. Remove the appliance front door (see
Removing Glass Encloslure panel on Page 32.
Step 2. Install decorative volcanic stone—
Sprinkle the decorative volcanic stone in a
pleasing pattern. The volcanic stone should
be placed directly on top of the firebox
bottom, along the front and to the back at the
right and left sides of the burner. Position any
optional ceramic fiber liners before placing
the stone. Logs should be positioned after
the volcanic stone.
Note: This appliance is provided with enough
Glowing Embers for several applications,
do not feel compelled to use all that is in a
new bag. For best glowing effect, replace
the ember material annually. Replacement
Glowing Embers are available (Catalog
Number 88L53).
Glowing Embers
Separate into Quarter
Size (separate) Pieces
Bag of Glowing
Embers (rockwool)
Figure 51
Step 3. Separate the Glowing Ember
(Rockwool) into pieces about the size of a
quarter (Figure 51). Keep the pieces fluffed
up, not matted. Distribute these pieces over
the front surface of the burner, as shown
in Figure 52. Do not use more than is
necessary. When properly positioned, the
Glowing Embers will cover approximately
65% of the front burner and with no
appreciable gaps or openings. Ensure that
the main burner ports remain uncovered by
the ember material.
Step 4. Placement of Logs—All top logs
that rest on lower logs, do so over notches,
indents or nubs. Proper log placement is
critical to prevent sooting. Logs should be
placed in the gaps between the flame peaks
and should be positioned so they do not
impinge the flames.
Step 5. Position the individual logs as shown
in Figures 57, 58 and 59. Logs should be
placed in the order shown. All logs that have
notches to fit over the grate tines should be
positioned with these notches directly against
the grate. Handle logs carefully to prevent
breakage.
Proper log placement is critical to encourage
outstanding flame appearance and prevent
sooting. When positioned properly as shown,
logs will be positioned between flame peaks
and will not impinge any flames.
Refer to Figure 53 for MPD33 Series
appliances, to Figure 54 for MPD35 Series
appliances and to Figure 55 for MPD40 and
MPD45 Series appliances.
28
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
REFERENCE
Firebox Accessories / Parts
Cat. No.Model No.Description
88L53FGEBag of Glowing Embers
80L42FDVS
Bag of Decorative
Volcanic Stone
Page 29
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
MPD33 LOG PLACEMENT
Log
Number Description (Stamped #)
1
3
2
Position the individual logs as shown below. Logs should be placed
4
6
5
in the order shown. Position the rear log on the brackets at the rear
of the firebox with the log's notches directly over the brackets.
Position the right log (log no. 3) by inserting the pin from the rear
log into the hole on its upper end. Place the left log and then the
smaller left and right top logs. All logs that have notches to fit over
the grate tines should be positioned with these notches directly
against the grate. All top logs that rest on lower logs, do so over
flattened mounting faces in the bottom logs.
1 Log, Rear (39-12)
2 Log, Left (39-1)
3 Log, Right (39-2)
4 Log, Top Center (39-13)
5 Log, Top/Left (39-3)
6 Log, Top/Right (39-4)
Catalog Number for the entire log set: 24M15
Proper log and twig placement is critical to encourage outstanding
flame appearance and prevent sooting.
1
4
3
2
5
6
Figure 53
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
29
Page 30
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
MPD35 LOG PLACEMENT
Log
1
3
2
Number Description (Stamped #)
1 Log, Rear (39-5)
2 Log, Left (39-1)
3 Log, Right (39-2)
4 Log, Top Center (39-6)
5 Log, Top/Left (39-3)
6 Log, Top/Right (39-4)
Catalog Number for the entire log set: H6197
4
5
6
Position the individual logs as shown below. Logs should be placed
in the order shown. Position the rear log on the brackets at the rear
of the firebox with the log's notches directly over the brackets.
Position the right log (log no. 3) by inserting the pin from the rear
log into the hole on its upper end. Place the left log and then the
smaller left and right top logs. All logs that have notches to fit over
the grate tines should be positioned with these notches directly
against the grate. All top logs that rest on lower logs, do so over
flattened mounting faces in the bottom logs.
Proper log and twig placement is critical to encourage outstanding
flame appearance and prevent sooting.
1
43
30
2
Figure 54
5
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
6
Page 31
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
MPD40 AND MPD45 LOG PLACEMENT
Log
1
2
3
Number Description (Stamped #)
1 Log, Center (39-8)
2 Log, Rear (138)
3 Log, Right (39-10)
4 Log, Left (39-9)
5 Log, Top/Left (39-11)
6 Log, Top/Right (39-11)
Catalog Number for the entire log set: 24M25
4
5
6
Position the individual logs as shown below. Logs should be placed
in the order shown. Position the center log on the burner first, then
place the glowing embers as shown in Figure 52. Place the rear
log, both the right and left, and then the smaller left and right top
logs. All logs that have notches to fit over the grate tines should
be positioned with these notches directly against the grate. All top
logs that rest on lower logs, do so over flattened mounting faces
in the bottom logs.
Proper log and twig placement is critical to encourage outstanding
flame appearance and prevent sooting.
1
4
3
2
Figure 55
5
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
6
31
Page 32
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Step 10. REMOVING AND INSTALLING
THE GLASS DOOR
WARNING
• Do not attempt to substitute
the materials used on these
doors, or replace cracked or
broken glass.
•Handlethisglasswith
extreme care! Glass is
susceptible to damage – Do
not scratch or handle roughly
while reinstalling the glass
door frame.
•Theglassdoorofthis
appliance must only be
replaced as a complete
unit as provided by the
manufacturer. Do not attempt
to replace broken, cracked or
chipped glass separately.
• Do not attempt to touch
the front enclosure glass
with your hands while the
fireplace is in use.
WARNING
Do not operate appliance with
the glass front removed, cracked
or broken.
AVERTISSEMENT
Ne pas utiliser l'appareil si le
panneau frontal en verre n'est
pas en place, est craqué ou
brisé.
Only doors certified with the appliance
shall be used.
Seules des portes certifiées pour cet
appareil doivent être utilisées.
WARNING: DO NOT abuse glass door by
striking or slamming shut.
32
Removing the Glass Enclosure Panel
(see Figure 56)
Remove the top louver assembly or radiant
panel. To access the glass door securing
latches, first open the lower control
compartment door (Figure 56 ) by pushing
in simultaneously the left and right top
corners of the door (the door is hinged at the
bottom).
Remove the bottom compartment door by
sliding the hinge pin, located at the door’s left
side, to the right until it disengages from the
left corner post hole. Pull the door diagonally
to the left, away from the fireplace.
Locate the two (2) latches at the top of the
control compartment and disengage them
from the door frame bottom vee-flange,
pulling down on their handles to open them.
Installing the Glass Enclosure Panel
(see Figure 56)
Retrieve the glass door. Visually inspect the
gasket on the backside of the frame. Gasket
surface must be clean, free of irregularities
and seated firmly.
Position the door in front of the firebox
opening with the bottom of the door held
away from the fireplace (Figure 56). Hook the
top flange of the door frame over the top of
the firebox frame.
Let the bottom of the door frame swing
gently in towards the fireplace ensuring that
the gasket seats evenly as the door frame
draws shut. Fasten the two latches located
underneath the firebox floor to the door's
vee-flange. Close both the latches securely.
Lower Compartment Door and Hinge
Glass
Door
Glass Door Frame
Bottom Vee-flange
Glass Door Latch
Figure 56
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Glass Door Frame
Top Flange
Firebox Floor
Step 11. BURNER ADJUSTMENTS
Flame Appearance and Sooting
Proper flame appearance is a flame that is
blue at the base and becomes yellowishorange in the body of the flame.
When the appliance is first lit, the entire
flame may be blue and will gradually turn
yellowish-orange during the first 15 minutes
of operation. If the flame remains blue, or if
the flame is orange with evidence of sooting
(black tip), the air shutter opening may need
to be adjusted.
If the air shutter opening is closed too far,
sooting may develop. Sooting is indicated
by black puffs developing at the tips of very
long orange flames. Sooting results in black
deposits forming on the logs, appliance
inside surfaces and on exterior surfaces
adjacent to the vent termination.
Sooting is caused by incomplete combustion
in the flames and lack of combustion air
entering the air shutter opening. To achieve
a warm yellowish-orange flame with an
orange body that does not soot, the shutter
opening must be adjusted between these two
extremes.
Air Shutter Adjustment Guidelines
• If there is smoke or soot present, rst
check the log set positioning to ensure
that the flames are not impinging on
any of the logs. If the log set is properly
positioned and a sooting condition still
exists, then the air shutter opening should
be increased.
• The more offsets in the vent system, the
larger the air shutter opening will need
to be.
• An appliance operated with the air shutter
opened too far, may have flames that
appear blue and transparent. These weak,
blue and transparent flames are termed
anemic.
• Propane models may exhibit ames
which candle or appear stringy. If this is
present and persists, adjust the air shutter
to a more closed position, then operate
the appliance for a few more minutes to
ensure that the flame normalizes and the
flames do not appear sooty.
The following chart is provided to aid you in
achieving the correct air shutter adjustment
for your installation.
Air Shutter Adjustment Guidelines
Amount of
Primary Air
If air shutter is
closed too far
If air shutter is
open too far
Flame
Color
Flame will
be orange
Flame will
be blue
Air Shutter
Adjustment
Air shutter
gap should be
increased
Air shutter
gap should be
decreased
Page 33
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
WARNING
• Air shutter adjustment should
only be performed by a
qualified professional service
technician.
• Ensure front glass panel are
in place and sealed during
adjustment.
CAUTION
• Soot will be produced if the
air shutter is closed too much.
Any damage due to sooting,
resulting from improperly
setting the air shutter, is not
covered under the warranty.
• The air shutter door and
nearby appliance surfaces
are hot. Exercise caution to
avoid injury while adjusting
flame appearance.
1. Refer to Figures 61, 62 and 63 for
proper flame appearance. To adjust
the flame, rotate the adjustment rod
toward the back or toward the front of
the fireplace (rod located in the lower
control area). Position the air shutter to
the factory setting as shown in the table in
Figure 60.
2. Light appliance (follow lighting procedure
on lighting label in control compartment
or in the Care and Operation Instructions).
3. Allow the burner to operate for at least
15 minutes while observing the flame
continuously to ensure that the proper
flame appearance has been achieved.
If the following conditions are present,
adjust accordingly.
• If ame appears weak or sooty, adjust
the air shutter, incrementally, to a
more open position until the proper
flame appearance is achieved.
• If ame remains blue, adjust the air
shutter, incrementally, to a more
closed position until the proper flame
appearance is achieved.
4. When satisfied that the burner flame
appearance is normal, reinstall the
lower control compartment door, then
proceed to finish the installation.
Figure 57: MPD33 MODEL
Figure 58: MPD35 MODEL
Figure 59: MPD40 AND MPD45 MODEL
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
33
Page 34
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
RIAYROTCAF
Burner Tube
Air Shutter
Adjustment Rod Down
(fully open position)
sledoM
MPDT33
MPDR33
MPD35
MPD40
MPD45
Figure 60
Adjusting Set Screw
Adjustment Rod Up
saG
epyT
.taN23/1)8.O(
.porP61/3)67.4(
.taN23/1)8.O(
.porP61/3)67.4(
.taN23/1)8.O(
.porP61/3)67.4(
.taN8/1)2.3(
.porP2/1)31(
.taN8/1)2.3(
.porP2/1)31(
(minimum air
opening position)
RETTUHS
GNITTES
)mm(in.
Step 12. HOOD INSTALLATION
Refer to Figures 65 and 66. All models
must have hoods installed prior to
operating.
On all Radiant Panel units, slide the hood into
the slots on the lower edge of the radiant panel
(Figure 62).
On louvered face units, slide the hood into
the slots on the lower edge of the cabinet top
(Figure 62).
FINISHING REQUIREMENTS
Wall Details
Complete finished interior wall. To install
the appliance facing flush with the finished
wall, position framework to accommodate
the thickness of the finished wall (Figures 65
and 66)
See Page 5 for
Cold Climate Insulation and
Page 8 for Clearances.
Combustible
Finished Wall
Materials
Combustible
material may
touch top of
appliance.
Combustible
materials
NOT allowed
below this point
on face
of appliance.
Hood must be installed as shown.
This area must remain
clear of combustible
materials.
Header
Spacing
Top Standoff
Top of Appliance
Radiant panel
Top of Door Frame
Figure 61: Radiant Panel Models
Combustible
Finished Wall
Materials
Combustible
material may
touch top of
appliance.
Combustible
materials
NOT allowed
below this point
on face
of appliance.
This area must remain
clear of combustible
materials.
Header
Spacing
Top Standoff
Top of Appliance
Louvers
Top of Door Frame
Min. 1 in.
(25 mm)
Min. 1 in.
(25 mm)
Hood must be installed as shown.
Figure 62: Louver Face Models
34
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Page 35
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
STEP 13. ATTACHING SAFETY-IN-OPERATION WARNINGS
It is the installer’s responsibility to ensure these warnings are properly affixed during installation. These warning labels are a
critical step in informing consumers of safe operation of this appliance.
ATTACHING SAFETY-IN-OPERATION
WARNINGS
It is required that the safety instruction labels
furnished with the fireplace be affixed to the
operation and control point of the fireplace. A
safety instruction label must be affixed to the
wall switch plate where the fireplace is turned
on and off (See Figure A) or wall thermostat
(See Figure B) and if used on the remote control
handheld transmitter (Figure C). To properly
complete the installation of this fireplace, locate
the multi-lingual adhesive labels provided with
the Care and Operation Instructions and proceed
as follows:
1. Locate the wall switch or wall thermostat
that controls the fireplace (verify the switch
operates the fireplace by turning it on and off).
Clean the wall switch plate or wall thermostat
thoroughly to remove any dust and oils. Affix
the label to the surface of the plate of the wall
switch that controls the fireplace (Figure A)
or the wall thermostat (Figure B). Choose
the language primarily spoken in the home. If
unknown, affix the English language label.
2. If a remote control is used to control the
fireplace, locate the transmitter and clean
it thoroughly to remove any dust and oils.
Affix the label to the surface of handheld
transmitter (Figure C). Choose the language
primarily spoken in the home. If unknown,
affix the English language label.
3. If you are unable to locate the labels, please
call Lennox Hearth Products or your nearest
Lennox Hearth Products dealer to receive
additional safety instruction labels free of
charge.
Cat. No. H8024 Replacement Label Kit
LENNOX HEARTH PRODUCTS
1-800-655-2008
Note: English is red text on clear label. French and
Spanish are white text on black label.
SAFETY LABEL
DIAGRAMS
APPOSITION DES MISES EN GARDE RELATIVES
À LA SÉCURITÉ D’UTILISATION
Il est impératif que les étiquettes de sécurité
fournies avec le foyer soient collées à côté des
dispositifs de contrôle du foyer. Une étiquette
de sécurité doit être collée sur la plaque de
l’interrupteur contrôlant l’allumage du foyer (voir
Figure A) ou sur le thermostat mural (voir Figure B)
et, le cas échéant, sur le boîtier
de la télécommande (Figure C). Pour achever
l’instal lation correcte de ce foyer, procédez
comme suit avec les étiquettes adhésives en
langues étrangères fournies avec les instructions
d’utilisation et d’entretien :
1. Repérez l’interrupteur ou le thermostat mural qui
contrôle le foyer (vérifiez que l’interrupteur
contrôle le fonctionnement du foyer en le faisant
basculer de Marche à Arrêt, et vice-versa).
Nettoyez soigneusement la plaque murale de
l’interrupteur ou le thermostat mural pour éliminer
la poussière et les traces de graisse ou d’huile.
Collez l’étiquette sur la surface de la plaque de
l’interrupteur mural qui contrôle le foyer (Figure A) ou du thermostat mural (Figure B). Choisissez
la langue qui est principalement parlée dans la
résidence du propriétaire. En cas de doute, collez
l’étiquette en anglais.
2. Si une télécommande est utilisée pour contrôler
le foyer, nettoyez la soigneusement pour éliminer
la poussière et les traces de graisse ou d’huile.
Collez l’étiquette sur le boîtier de la télécommande (Figure C). Choisissez la langue qui
est principalement parlée dans la résidence du
proprié taire. En cas de doute, collez l’étiquette
en anglais.
3. Si vous ne trouvez pas les étiquettes, veuillez
appeler Lennox Hearth Products ou votre
distribu teur Lennox Hearth Products local
pour recevoir gratuitement des étiquettes
supplémentaires.
Étiquettes de remplacement, n° cat. H8024
LENNOX HEARTH PRODUCTS
1-800-655-2008
Remarque : Le texte anglais est rouge sur un support
transparent. Le texte français et espagnol est blanc
sur un support noir.
DIAGRAMMES DES ÉTIQUETTES
DE SÉCURITÉ
COLOCACIÓN DE ADVERTENCIAS DE
SEGURIDAD EN OPERACIÓN
Se requiere que las etiquetas de instrucciones de
seguridad incluidas con la chimenea se coloquen en
el punto de operación y control de la misma. Se debe
colocar una etiqueta de instrucciones de seguridad
en la placa del interruptor de pared desde el cual se
enciende y se apaga la chimenea (ver la Figura A)
o en el termostato de pared (ver la Figura B) y en
el transmisor de control remoto (Figura C) si se
usa. Para completar correctamente la instalación de
esta chimenea, encuentre las etiquetas adhesivas
multilingües incluidas con las instrucciones de
cuidado y operación y haga lo siguiente:
1. Identifique el interruptor o el termostato de
pared que controla la chimenea (verifique que el
interruptor opera la chimenea encendiéndola y
apagándola). Limpie bien la placa del interruptor o
el termostato
de pared para quitar el polvo y aceite. Pegue la
etiqueta en la superficie de la placa del interruptor
que controla la chimenea (Figura A) o en el
termostato de pared (Figura B). Seleccione el
idioma que más se habla en la casa. Si no sabe
cuál es, use la etiqueta en inglés.
2. Si se usa un control remoto para controlar la
chimenea, encuentre el transmisor y límpielo bien
para quitar el polvo y aceite. Pegue la etiqueta en
la superficie del transmisor (Figura C). Seleccione
el idioma que más se habla en la casa. Si no sabe
cuál es, use la etiqueta en inglés.
3. Si no puede encontrar las etiquetas, sírvase
llamar a Lennox Hearth Products o al distribuidor
de Lennox Hearth Products más cercano para
recibir etiquetas de instrucciones de seguridad
adicionales gratuitas.
Juego de etiquetas de repuesto - Nº de cat. H8024
LENNOX HEARTH PRODUCTS
1-800-655-2008
Nota: La etiqueta en inglés es transparente con texto
rojo. Las etiquetas en francés y español son negras
con texto blanco.
DIAGRAMAS DE ETIQUETAS
DE SEGURIDAD
Illustrations are for example only. Your
accessories may be different.
Les illustrations sont par exemple
uniquement. Vos accessoires peuvent
être différents.
Las ilustraciones son sólo ejemplos.
Tu accesorios pueden ser diferentes.
Figure A
Figure BFigure C
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
35
Page 36
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
S
e
a
l
a
n
t
INSTALLATION ACCESSORIES
Listed Secure Vent® Components
Cat. No.ModelDescription
H1968SV4.5HT-2Horizontal Square
Termination with
Firestop/ Spacer (H2246)
and Adaptor (74L61)
H2152SV4.5CGV-1Vertical Termination Cap,
High Wind
94L10*SV4.5HTSSHorizontal Small Square
Termination with
Firestop/Spacer (96K80)
and Adaptor (74L61)
98L27*SV4.5HTSSL Horizontal Small
Square—Long Termination with Firestop/Spacer
(96K80) and Adaptor
(74L61)
17M52SV4.5HGS-1Termination Guard,
Square (1 pack)
(Ref. Instr. #750109M)
17M53SV4.5HGS-12 Termination Guard, Hori-
zontal Square (12 pack)
(Ref. Instr. #750109M)
87L02SV4.5HGSTermination Guard for
Horizontal Square Termination (Deluxe) (1 pack)
(Ref. Instr. #750055M)
Vent Sections
(Rigid)
Listed Secure Vent® Components
Cat. No.ModelDescription
77L70SV4.5L66 Inch (152 mm)
77L71SV4.5L1212 Inch (305 mm)
77L72SV4.5L2424 Inch (610 mm)
77L73SV4.5L3636 Inch (914 mm)
77L74SV4.5L4848 Inch (1219 mm)
77L75SV4.5LATelescopic Length Slip
Section (2 in. to 7–1/2 in.
rigid)
77L76SV4.5E4545 Degree Elbow
77L77SV4.5E9090 Degree Elbow
10K81SFMPMill-Pac, Black, High-
Temperature Sealant
89L40SFMP-12Mill-Pac, Black, High-
Temperature Sealant,
Bulk 12 pack
99L02SV4.5HRK14 Horizontal Riser Kit,
14 in., (Ref. Instr.
#750146M)
99L03SV4.5HRK36 Horizontal Riser Kit,
36 in., (Ref. Instr.
#750146M)
96K93SV4.5SUSupport Strap
H5820SV4.5HTSKTermination Shroud
(Guard) for Horizontal
Square Termination
(1 pack)
(Ref. Instr. #750246M)
H3907SV4.5ARSAAttic Insulation Shield
with adjustable height,
12 in.–22 in.
H1988CTSA-33Chase Top Shroud Kit,
Arch Top 3 X 3 Ft.,
(Ref. Instr. #750194M)
H1985CTSO-33Chase Top Shroud Kit,
Open Top 3 X 3 Ft.,
(Ref. Instr. #750193M)
H1987CTSO-44Chase Top Shroud Kit,
Open Top 4 X 4 Ft.,
(Ref. Instr. #750193M)
H1986CTSO-46Chase Top Shroud Kit,
Open Top 4 X 6 Ft.,
(Ref. Instr. #750193M)
H5816SV4.5-
TWSK10
Through Wall Shield Kit
(used to shield the
direct-vent pipe from
blown insulation)
(Ref. Instr. #750247M)
The following flashings come packaged with a storm collar:
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
INSTALLATION ACCESSORIES CONTINUED
Listed Secure Flex® Components
Cat. #ModelDescription
These termination kits include firestop/spacer, gear clamps and flex adaptor.
60L10SF-1818 feet (5.49 m) *
98K03SF-1212 feet (3.66 m)*
H2248SF4.5HF-10Firestop / Spacer—
H2249SF4.5VF-10 Firestop/Spacer—Vertical,
56L74SFVT30
56L75SFVT45
91L66SFGC4-6Gear Clamp 4.5 in. (114 mm)
91L67SFGC7-6Gear Clamp 7.5 in. (190.5
H7748H7748
compressed ex
(Ref. Instr. #750053M)
compressed ex
(Ref. Instr. #750052M)
Horizontal, ex (3-1-1
spacing), 10 Pack
ex (1-1-1 spacing), 10 Pk
Vertical Termination for ex
(flat to 6/12) with flex adaptor,
section of rigid vent, roof
support collar assembly, roof
flashing and storm collar.
(Ref. Instr. #750052M)
Vertical Termination for ex
(6/12 to 12/12) with flex
adaptor, section of rigid
vent, roof support collar
assembly, roof flashing,
and storm collar.
(Ref. Instr. #750052M)
for ex (6 pack)
mm) for ex (6 pack)
36 in. Flex Connector
Kit. 36 in. of flex with
two adaptors for mating
two rigid sections of vent
together.
Listed Secure Flex® Components
Cat. #ModelDescription
H1969SF4.5HT-2Horizontal Square Termina-
77L87SFKIT12S
77L88SFKIT18S
77L89SFKIT24S
77L90SFKIT36S
77L91SFKIT48S
94L04* SFKIT12SS Small Square Termination for
94L05* SFKIT18SS Small Square Termination for
94L06* SFKIT24SS Small Square Termination for
94L07* SFKIT36SS Small Square Termination for
94L08* SFKIT48SS Small Square Termination for
94L09*SF-HTSSHorizontal Small Square
tion for ex (without flex
vent)
Square Term. for ex
(with 12 in. [305 mm]
compressed flex vent**)
Square Term. for ex
(with 18 in. [457 mm]
compressed flex vent**)
Square Term. for ex
(with 24 in. [610 mm]
compressed flex vent**)
Square Term. for ex
(with 36 in. [914 mm]
compressed flex vent**)
Square Term. for ex
(with 48 in. [1219 mm]
compressed flex vent**)
ex, with 12 in. (305 mm) of
compressed flex vent**
(Ref. Instr. #750204M)
ex, with 18 in. (457 mm) of
compressed flex vent**
(Ref. Instr. #750204M)
ex, with 24 in. (610 mm) of
compressed flex vent**
(Ref. Instr. #750204M)
ex, with 36 in. (914 mm) of
compressed flex vent**
(Ref. Instr. #750204M)
ex, with 48 in. (1219 mm)
of compressed flex vent**
(Ref. Instr. #750204M)
Termination for ex, without
flex vent (Ref. Instr. #750204M)
*Only for use with MPDT33 and MPD35 models.
**All compressed flex vents can be expanded up to two times.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
37
Page 38
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
GAS CONVERSION KITS
WARNING
This conversion kit shall be installed by a qualified service agency in
accordance with the manufacturer’s instructions and all applicable codes
and requirements of the authority having jurisdiction. If the information in
these instruction is not followed exactly, a fire, explosion or production of
carbon monoxide may result causing property damage, personal injury
or loss of life. The qualified service agency is responsible for the proper
installation of this kit. The installation is not proper and complete until the
operation of the converted appliance is checked as specified in the manufacturer’s instructions supplied with the kit.The qualified service agency
performing this installation assumes responsibility for this conversion.
AVERTISSEMENT
Cette trousse de conversion doit être installée par un technicien agréé,
selon les instructions du fabricant et selon toutes les exigences et tous les
codes pertinents de l’autorité compétente. Assurez-vous de bien suivre
les instructions dans cette notice pour réduire au minimum le risque
d’incendie, d’explosion ou la production de monoxyde de carbone pouvant
causer des dommages matériels, des blessures ou la mort. Le tecnicien
agréé est responsable de l’installation de cette trousse. L’installation n’est
pas adéquate ni complète tant que le bon fonctionnement de l’appareil
converti n’a pas été vérifié selon les instructions du fabricant fournies avec
la trousse. Le fournisseur de service qualifié ayant réalisé l'installation
assume les responsabilités liées à la conversion.
Step 1. TURN OFF THE GAS SUPPLY TO THE
APPLIANCE and disconnect power supply at
the circuit breaker. Ensure appliance is cold.
CAUTION: THE GAS SUPPLY SHALL BE
SHUT OFF PRIOR TO DISCONNECTING
THE ELECTRICAL POWER, BEFORE
PROCEEDING WITH THE CONVERSION.
In Canada:
THE CONVERSION SHALL BE CARRIED
OUT IN ACCORDANCE WITH THE
REQUIREMENTS OF THE PROVINCIAL
AUTHORITIES HAVING JURISDICTION
AND IN ACCORDANCE WITH THE
REQUIREMENTS OF THE CAN/
CSA-B149.1 INSTALLATION CODE.
LA CONVERSION DEVRA ÊTRE
EFFECTUÉE CONFORMÉMENT AUX
RECOMMANDATIONS DES AUTORITÉS
PROVINCIALES AYANT JURIDICTION
ET CONFORMÉMENT AUX EXIGENCES
DU CODE D'INSTALLATION CAN/
CSA-B149.1.
Gas conversion kits are available to adapt
your appliance from the use of one type of
gas to the use of another. These kits contain
all the necessary components needed to
complete the task including labeling that
must be affixed to ensure safe operation.
Kit part numbers are listed here and the
following steps detail the conversion
procedure. Refer to the instructions provided
with the conversion kit when performing any
gas conversion.
ATTENTION: AVANT D’EFFECTUER
LA CONVERSION, COUPEZ D’ABORD
L’ALIMENTATION EN GAZ, ENSUITE,
COUPEZ L’ALIMENTATION ÉLECTRIQUE.
Step 2. Open the lower control compartment
door (see Figure 48 on Page 27) by pushing
on the right top corner of the door (the door
is hinged at the bottom).
[Optional] Remove the control compartment
door by sliding the hinge pin, located at the
door’s left side, to the right until it disengages
from the left corner post hole. Pull the
control compartment door diagonally to the
left, away from the fireplace.
Step 3. Remove the front glass door/frame
from the appliance (see Page 32).
38
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Page 39
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Pilot
Orifice
Pressure
Regulator
Remove
These
Components
Step 4. Carefully remove the logs. Exercise
care so as not to break the logs.
Step 5. Refer to Figure 2 on Page 4.
A. Remove the sub floor.
B. Remove the two (2) screws securing the
burner assembly.
C. Remove the burner assembly with
attached venturi tube.
Millivolt and Electronic Ignition
System Appliances
Step 6. SIT Systems—Refer to Figure 63
and the instructions provided with the SIT
Regulator Conversion Kit. Using a Torx
T20 driver (with 1/4 in. shank and center
hole) or slotted screwdriver, remove and
discard the pressure regulator mounting
screws (two screws for electronic models,
three screws for millivolt models), pressure
regulator tower, the diaphragm assembly
(if applicable) and the spring. Discard all
removed components.
Step 7. Install the new pressure regulator
assembly using the supplied screws as
shown in Figure 63. Tighten the screws to
25 in-lb..
Step 9. Refer to Figure 64 and replace the
pilot orifice.
Figure 64: Electronic Pilot
Remove the pilot hood assembly to access
the hexed pilot orifice. Remove and replace
the orifice with the one provided with the kit.
Exercise extreme care to prevent damage to
or breakage of the igniter assembly.Step 10.
Refer to Figure 64 and replace the burner
orifice.
A. Remove the orifice from the manifold and
replace it with the one provided in the kit. See
the following table for orifice sizes for natural
and propane models. Figure 65 illustrates
the orifice.
Step 13. Turn on gas supply and test for gas
leaks (refer to Page 27).
Step 14. Relight the main burner. The lighting
instructions can be found on the lighting
label in the control compartment or in the
Care and Operation Manual provided with
the appliance. Verify proper burner ignition
and operation. See Burner Adjustments and
Burner Flame Appearance on Page 33.
Inspect the pilot system for proper flame. The
pilot flame should engulf the flame sensor as
shown in Figure 50 on Page 27.
Step 15. Using a manometer, test the inlet
and manifold gas pressures. See Table 3 on
Page 4.
ALWAYS TEST PRESSURES WITH THE
VALVE REGULATOR CONTROL AT THE
HIGHEST SETTING.
Model
Series
MPDT33
MPDR33
MPD35
MPD40
MPD45
Nat.Gas
drill size (inches)
#37 (0.104 in.)*
24M10•
#45 (0.0820 in.)*
39L66•
#38 (0.1015 in.)*
99K76•
#47 (0.0785 in.)*
99K74•
* Standard size installed at factory
• Part /Cat. Number
Propane
drill size (inches)
0.048 in.
99K78•
#55 (0.0520 in.)*
19L52•
0.063 in.
21L01•
#52 (0.0635 in.)*
37G00•
Table 10: Burner Orifice Sizes
Elevation 0–4500 ft ( 0–1372 m)
Millivolt Valve
Electronic Valve
Figure 63
Step 8. Install the enclosed identification
label to the valve body where it can be easily
seen.
Figure 65
Use pipe joint compound or Teflon tape on
all pipe fittings before installing (ensure
propane resistant compounds are used in
propane applications, do not use pipe joint
compounds on flare fittings).
B. Retrieve the burner and hold the venturi
tube above the orifice. Place the shutter
adjusting rod in the propane slot of the
shutter arm (see Figure 60 on Page 34).
Set the burner assem bly into its position
and secure the trapezoidal plate with the two
screws previously removed.
C. Reinstall the baffle with the two baffle
securing screws.
Step 11. Reassemble the remaining
components by reversing the procedures
outlined in the Steps 1–7.
Step 12. Attach the conversion label provided
in the conversion kit next to the rating plate
on the appliance.
39
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Page 40
LENNOX HEARTH PRODUCTS • MERIT PLUS® DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Lennox Hearth Products reserves the right to make changes at any time, without notice, in design,
materials, specifications, prices and also to discontinue colors, styles and products.
Consult your local distributor for fireplace code information.
LENNOX®, the LENNOX design, DAVE LENNOX, the image of DAVE LENNOX and other related
LENNOX marks are registered or common law trademarks of Lennox Industries Inc. and are used
with permission.